I know about the Gacha, but is it even worth using? Should I be using Flower Gems to upgrade my Unit and Equipment storage instead?

I ask this because rolling a 5* from gacha seems worthless as you get 5*'s from events with dress blooms and skill blooms, and sometimes even equipment. The only reason I could even fathom on rolling Gacha is for a 6* which even without equips would be higher than Event 5*'s. But at 0.5% chance, even rolling 50 gems for 11 chances, only give about a 5.5% probability of a 6*.

Am I wrong to think this way? Is there something I'm missing?

(I already have my waifu, my good ol' 3* Jasmine)