You’ve already been given some great advice. I’ll just +1 with what they’ve said.
It’s tempting to jump to the shiny 5*s but most aren’t as strong at 3/70 as maxed 4’s… better to get a nice set of 3s and 4s before working on those 5s. Get some mats accumulated. Get some experience under your belt with raids and wars. Then you’ll have a better idea of who you want to spend the mats on.