When leveling, I often prioritize BP and if I need more of the other stats I equip the badges that use 3bp for 3 hp or fp.

I often save the star points to use Sweet Treat which is a reasonably reliable heal if you can get good at it. In certain situations I’ll use the other star powers for high damage.

I regularly switch which characters I’m using and their builds depending on the enemies in the area. Do you need high single target damage or AOE? Are there fliers? Are there spiky things?

Gombella is not bad early game and Koops is quite good IMO. Koops can hit all grounded enemies at once, which is very useful AOE, and Goombella has some decent jumping single target damage.

I feel like a lot of this advice also applies to Expedition 33.

You should only need to use tattle at most once per enemy type, I’m not sure why you would use it after that.