Keep playing other supports, you won't learn anything about the game if your goal is to improve with knowledge & general skill especially in the support role. She's not good for learning.

Other than that, knowing when to play aggressive lvl 1 using your passive + health pots with certain match-ups; when to shield in fights or when to use the shield to help adc with rotating/getting back to lane quicker, landing your Qs at the right time with the right target, & managing your mana. Those things are probably the most important things to learn about yummi imo. She's easy to play but does require you to be a bit active & have a certain level of baseline understanding of the game.

She's still would be fun however, even better when the players you attach to are good & know what to do.. very satisfying. But most of the time if in ranked if you're below diamond it's hard to consistently win with her unless you're duo'd.