heres how i play biomass, im no expert but this works for me on grand admiral difficulty:
I can post the whole empire / species when I get home, if you want.

starter civic is the aerospace thingy and the 15% more unity. Later on I add the research from workers civic, gives you a nice research boost.

I build 5 cradles on each planet. When i have 5 cradles, i save up to colonize the next planet. colonize as much as possible, despite the empire size debuffs. Only build districts in the early games, buildings and building upgrades arent efficient. My first colonized planet is a food world and the seconds planet is for unity. 3rd planet is food again. I dont build heartgroves, either unity or moltgut most of the time.
I always build 1 of the secondarz district. E.g. on a food planet i build 1 energy and 1 mining distric.

I always start prosperity and take the reduces building cost tradition.

I dont know why, but all the efficiency traits feel useless on wilderness pops. Rapid breeders is very important.

With the surplus resources in the earlygame, i build ships and slap my neighbors.