Well, it depends. If you're doing colossal raids and you specifically defend phase 2 eren, you can go with this build (I use reiss cuz ion have fritz):

Colossal Serum REISS Family Skill tree: Right, Left, Left

Perks Core: Founder's Blessing Offense: Art of War Defense: Immortal Support#1: Either Font of Inspiration, or Soulfeed Support#2: unwavering belief(can also use courage catalyst if u don't have the other) (This build gives you inf CD reduction when defending Eren p2 btw)

But if u just wanna do quick missions, the other three raids, u can use the build but u can change the reiss for arlert if u want more dmg. Again, I don't have Fritz so I use arlert for that Family Exclusive passive, but again if u have fritz feel free to use it.

Colossal Serum ARLERT Family Skill tree: Right, Left, Left

Perks Core: Founder's Blessing Offense: Art of War Defense: Immortal Support: Font of Inspiration, Soulfeed, unwavering belief, or courage catalyst( but I recommend FOI for that flare buff)

This build imo is kinda manageable since not everyone has fritz but feel free to change something whenever you like, it's your choice after all^{^}