In Yu-Gi-Oh! GX, someone takes Yugi's deck and copies his look. His hair leaves much to be desired.
In Sailor Moon, Zoisite, one of the Shitennou, dresses up as Sailor Moon, saves people from accidents he sets up himself, and stages his own kidnapping to trap the real one. However, red highlights are blue on the fake costume. (It happens in the Sailor Moon Plus fan game, too, in which he also adopts Sailor Moon's move set.)
Dragon Ball Z had the "historic" recreation of the Cell Games with the actors wearing plastic masks that had the yellow Super Saiyan hair.
In Galaxy Angel, all the fake Angels have perfect costumes, but, besides the fake Milfeulle, they are also all Gonks and look completely different from their counterparts. (The Galaxy Angel gameverse versions were almost exact copies, but a sharp eye could tell them apart anyway.)
One of Maron's heists in Kamikaze Kaitou Jeanne gets complicated when her Transformation Trinket ends up in the hands of the possessed Victim of the Week. Her makeshift disguise includes an altered yukata, a (much, much plainer) handmade cross, hair extensions, and spray-on hair dye. Things get even more complicated when she gets caught in a Drowning Pit, the dye washes off, and the hair extensions float away.
In an early story arc, Spidey's costume gets trashed (again), but he doesn't have a spare and is forced to buy a Spider-Man costume from a costume shop. A dunk in the river causes the cheap costume to shrink, forcing him to web it in place, which leads to further problems...
During a Team-Up with Wolverine, Spidey once found himself abroad and in need of a costume. Luckly for him he was able to purchase a reasonable imitation of a Spider-Man costume in a costume shop in Berlin. Unfortunately it had "Die Spinne" written on the back, the name that the character was known by and that Spider-Man comics were sold under in Germany back then.
Worth noting that Spidey's normal costume at the time was the black & white number, so it wasn't a "resonable" imitation to his way of thinking since it looked like his then-retired red-and-blue costume.
The Scarlet Spider outfit started out like this. This may be where the "stenciled sweats" idea came from in the movie.
The Steel Spider began as a boy in a Spider-Man Halloween costume with (non-functional) aluminum arms coming off the back. He eventually developed his own, still Spider-Man–based identity.
In The Spectacular Spider-Man, the Chameleon was a pretty convincing Spidey, except for the fact that Pete had switched to the black costume at this point. Oh, and the Chameleon had some weak imitations of the webbing, really hammed it up with the voice, and had an "insect early warning sense".
In Ultimate Spider-Man, Spidey had lost his costume to the Venom suit and was forced to wear a rag-tag Spidey t-shirt/blue pants combo and a loose mask. The glass piece that covered one eye of the mask fell out, and the lady he saved accidentally stepped on it.
Miles Morales, the second Ultimate Spider-Man, started off in a ratty store-bought Spider-Man costume that was given to him by his friend Ganke. He later upgraded to a cooler, more official model designed by Nick Fury.
Back in the very early Steve Ditko days, Peter Parker made his own costumes. The design was silk-screened on. And there was webbing between his arms and his side, which was a real pain to sew on.
The newspaper Amazing Spider-Man had a storyline where someone stole Spidey's costume and Peter himself fought crime in a Western mashup costume under the name of "Justice Guy".
At one point at least, Spidey bought a Halloween costume from a store and found it was better than his current costume.
During one part of The Clone Saga, Peter once again found himself without a costume. He improvised with the tank-top and pants he'd been wearing in prison, a leather jacket, and the black mask, boots, and gloves left over from his cloth version of the symbiote costume (wearing his webshooters on the outside for some reason). Can be seen at the bottom of the page here
In the Daredevil comics, Gladiator used to be the owner of a costume shop that specialized in superhero and supervillain costumes (the place looked kinda like a Wax Museum Morgue). He alters a DD costume for Foggy Nelson that looks pretty darn good for a knockoff. Except for the plastic prop billyclub, of course...
In the "Born Again" arc, the Daredevil impostor hired by the Kingpin had such a convincing costume (also made by the Gladiator), the real Daredevil actually stole it from him and put it on himself. Of course he had no choice as all of his other costumes had been destroyed.
Another impostor, an actor claiming to have been Daredevil for publicity, also had a perfect costume.
D-Man's "costume" consists of a copy of Daredevil's old yellow outfit and a knock-off Wolverine mask.
In The DCU, Nightwing had a "rival" hero called Nite-Wing with a 'costume' that consisted of a hockey jersey and combat pants.
Molly Hayes of Runaways tried to make her own costume with a T-shirt cape and cheap mask. This lasted a few seconds before Gert yanked the mask off herself.
Rorschach's costume in Watchmen is something of an inversion; he works in a tailor's shop in his day job and has the skills and equipment make himself any costume his imagination could devise -it's possible he made Nite Owl II's in exchange for thatrope gun - yet is content with a fairly low-key Coat, Hat, Mask ensemble with the mask coming from a fabric offcut that nobody at work wanted. It's probably the scariest costume in the comic. The pinstripe suit and shoes that he normally wears under it were probably quite expensive when they were new, for that matter.
After he escapes from prison he doesn't have time to do more than grab his coat, hat, mask and scarf over what he was wearing at the time, which definitely makes him fit the trope more.
Doctor Manhattan's "costume" consists of a circle emblem he inscribed in his forehead representing a hydrogen atom, plus whatever concessions to the sensibilities of ordinary humans he feels like making at the time... the ultimate in cheap costumes. He's perfectly happy to go around with Lower Manhattan hanging out, but people tend to complain.
Towards the end of the Birds of Prey series, former Batgirl Barbara Gordon met with a teenage girl who was co-opting her old identity. The cheapness of the young lady's costume - the cape and cowl of which were made from binliners - became a plot point, when it was what led Babs to figure out that she was homeless.
In Kick-Ass, a few of the costumes are pretty lame. It's kind of the point.
Harley Quinn's costume was just something she stole from a costume shop. The Joker's duds may count as well, given he just wears a ratty old suit. This tends to fall into Depending on the Writer at times. In Salvation Run, Joker mentions that his famed purple tuxedo is made of pure velvet.
The Creeper's rather ... flamboyant ... costume is explained in at least one version of his origin story as being odds and ends he put together from the leftovers nobody wanted to rent from a costume shop. Then he realized it creeped the bad guys the hell out, and decided to run with that theme.
At one point when Tony Stark had retired from his Iron Man identity to recover from his alcoholism, Tony had his "Recovery Armor" (basically a modernized Mark I armor) discovered by Dr. Demonicus and taken for a test run. Tony had to scrounge up costume parts of his teammates' within the Avengers West Coast so he can go out and get the armor back. Hawkeye mockingly named him "Spare Parts Man".
Later on in the story, Darkwing confronts the thief while wearing a Mardi Gras mask, with a luchador's mask underneath. The thief steals both of those masks anyway, leaving Darkwing unmasked again. After a few other disgruntled superheroes capture the mask thief, Darkwing reveals that it had all been a Batman-Gambit, and that he was actually wearing a mask of his secret identity over one of his spare regular masks in order to keep his secret identity safe. Launchpad and Gosalyn are befuddled.
During a time when his costume was confiscated by the U.S. Government due to accusations of treason against the nation, Captain America was provided an improvised costume that eliminated the stars & stripes of his regular outfit.
In Dial H, Nelson has to rescue a friend without a working Hero Dial, and creates his own blue-collar-worker-themed "Rescue Jack" superhero identity with a thrown-together costume and metalworking tools as weapons.
In Static Shock: Rebirth of the Cool, Static makes an approximation of his cartoon outfit out of some clothing stolen from a sporting goods shop. He later ditches it after several of his friends claim it makes him look like Ash from Pokémon.
Subverted with the Joker, who denies that his suit was cheap, and it's later confirmed to be entirely custom-made, though he apparently also doesn't believe in washing it. He also implies that the suit was created from the money he stole in the beginning of the film.
In The Dark Knight Rises, when Bruce Wayne needs to take Batman out of retirement quickly, he just slips on a ski mask.
The first Spider-Man movie had Peter Parker in his first costumed appearance with stenciled sweats and off-the-shelf gloves, mask and shoes. The novelization of the Spider-Man 2 movie revealed that Peter got his proper costume made by a guy who specialized in wrestling costumes. In the unfilmed James Cameron movie script, stores began selling Spider-Man costumes based off of what they saw him wearing. Peter ruined his costume and decided to buy the store costume because it was actually of better quality.
The "heroes" of Mystery Men all upgrade their costumes to something more impressive before the final battle.
Woody Harrelson's costume in Defendor (misspelling intentional)
Done in Kick-Ass, where some of the costumes are really cheesy. And yet the title character makes a wetsuit look downright awesome.
In Super, the Crimson Bolt's costume is clearly homemade and is pretty sloppy looking.
David Dunn's "Costume" in Unbreakable is a simple poncho. He probably didn't mean for it to be his superhero outfit; it just happened to be what he was wearing on the rainy night that he made his first foray into crimefighting.
Captain America: The First Avenger: Once Steve Rogers is turned into a Super-Soldier, he's put into USO shows while wearing a sloppily-made version of the Captain America outfit (though it is faithful to the character's appearance in the comics...). However, once he gets his new costume for actual missions, Steve personally sees to it that the outfit is based on the USO costume.
In general, it's oddly common in films for superheroes to start the movie with a sort of "dime store" version of their iconic costumes, then to switch at some point to their proper costumes. Spider-Man and Captain America were already mentioned. Iron Man builds an actual iron exosuit in a cave (WITH A BOX OF SCRAPS!!!!), and he manages to create a simplified, silver version of his iconic outfit before getting to the main movie costume.
Chronicle features Andrew Detmer making a cheap but fairly effective supervillain disguise out of his dad's firefighting gear and gas mask. Unfortunately, because he wears his school backpack over the coat, the neighbourhood thugs recognize him almost immediately. Not that it does them any good.
The Animorphs' morphing outfits (which have to be tight to work) are made up of bike shorts, tight T-shirts, and gymnastics uniforms. Marco was not impressed.
Live Action TV
Buffy the Vampire Slayer's Season 2 episode "Lie To Me" also utilizes this trope. The episode features a gang of (literal) vampire wannabes, all of whom dress to emulate movie vampires. While some of the teens are fairly convincing, about half are sporting cheap Halloween getups. Confronted with the gang's ringleader (who is wearing a blue polyester cape and ruffled cravat), Buffy quips, "My God—could you have a dorkier outfit?"
Also subverted, rather humorously, in the same episode: as Angel enters a Goth club, he scoffs that the clubgoing teens are completely ignorant of how real vampires dress; almost immediately, he comes face-to-face with a young man dressed identically to himself!
In Tales of the Starbuck Avenger, the titular heroine's costume consists of a cheap tiara, a javelin, and a Starbucks apron worn backwards as a cape.
In the Whateley Universe, the first outfit for Jinn Sinclair is made from stuff Jade Sinclair was able to find in dumpsters and steal from seconded lots in the backs of stores.
In The Inexplicable Adventures of Bob!, when Bob gains Super Powers, he cobbles together a costume that doesn't look very impressive. When he later loses said powers, he comments that his one regret is that he used a permanent laundry marker to make the "B" logo on a perfectly good shirt.
Spinnerette's first costume is composed of three store-bought Venom costumes stitched together (well, one costume, plus the arms of two more, really). She changes it after Marvel sends her a Cease and Desist order.
Static Shock: When the title character lost his mask while fighting a pair of bounty hunter villains, he grabbed a bandanna out of a nearby dumpster and tied it over his face, leading to derisive cowboy jokes from his foes.