Earn Your Happy Ending: The moral of the episode, and in the process her realization that she's talented in art perhaps without even thinking about it it opens many doors to Jan's future. (In future Brady incarnations, Jan following in Mike's footsteps used this talent to study architecture, and per the series' bible, has taken over as lead partner in the firm with her stepfather.)
High Hopes, Zero Talent: Jan's ability to dance. When she is asked by her teacher to seriously consider withdrawing from her dance class because of her lack of ability, she also takes up tap dancing but isn't much better at this.
Let The Wookie Win: The other siblings attempts to boost Jan's confidence by allowing her to "win" at darts, basketball, table tennis and Monopoly.
Life Imitates Art: Literally, as in real life, Eve Plumb is a talented painter. She painted the still life that would be used as a prop for the scenes where Jan is auditioning for a one-act play ... and that painting would play a key role in unlocking her future.
No Challenge Equals No Satisfaction: Jan's reaction once Cindy accidentally lets slip why she's having a perfect win-loss record lately. Mike and Carol point this out to the kids that letting someone win doesn't really help build their skills, only a false sense of self-esteem.
School Play: Jan tries to find her talent at acting by auditioning for a one-act play (about a struggling artist who is being harassed by bill collectors). She fails miserably.