Team Play : what combos are possible and effective?

[Equilin]

I just starts playing multi with one of my friends and we just tag together (vs wouldnt be fun cuz my playtime is much more). I want to try new stuff not possible in SP and want to ask if anyone has sth to share.
Atm we just used Interfaith Dialogue to bump science, and gift UUs for better upgrades.
No mods used.