At first I would recommend you to read Sanahtling's guide. --> https://docs.google.com/document/d/19K_dU3rCief_ajPGS9YBuVdxXBYFyCGGXAxYYyK0jzg/edit#heading=h.rixe84gs0hcx"]https://docs.google.com/document/d/19K_dU3rCief_ajPGS9YBuVdxXBYFyCGGXAxYYyK0jzg/edit#heading=h.rixe84gs0hcx
If you are rerolling then reroll until you get Sol, Amaterasu, Gaia, 2 SSR Kamihime from same element or 100% attack eideleon and then invest as much as you can/want!
Raiko is better then Tyr because she gets a -15% Attack A-Frame and in a Thunder Team you need Sol because we don't have a SSR Thunder healer at the moment.