To answer your question, I’d say that you start with Red Hood as the healer anchor to your team and work out from there.
For tanks, you could consider Aegir, Misandra, Drake, and Viv. Everyone hates on Aegir, but I believe that’s mostly because people think about the pre-release stats and think about what could have been. I’ve been told by people I believe that Aegir is an excellent tank. The others could be used, but I think you’ll probably get the most out of Aegir.
That leaves Green, purple, and yellow for your strikers. Lianna is far and away your best green. For your first purple, I would go with Sartana all the way. She hits hard, is fast, and is tough to kill. Victor could be a good choice also, but I think he’s more situational. Sartana is good at everything. Drake for yellow, to give you more area of effect punch. Plus the blind is great.
tl;dr - Lianna, Red Hood, Aegir, Drake, Sartana
All that said, I’m not sure where you are in terms of building up your team. I would suggest taking a portion of Radar’s advice and work up a solid 4* core rainbow team (if you haven’t already) before investing in all those 5s. You’ll get further faster by having a solid 4 core to get better titan scores and therefore more ascention mats for your eventual 5* team.