As a starter for 10 I would level up some of your 3* heroes to get a decent team for tournaments etc. Not sure why you would want to keep 5 x Belith as good as she is.
My thinking was to finish my red team ( lvl 3) which I’ve done, Now working on green, and work on a team to defeat monthly Legendary for ascension mats, I get to lvl 8/9 depending.
It all depends how you want to play this game. Some will focus on individual colour heroes others will focus on rainbow teams. I think it’s best to work on a rainbow team to give me more options for war, raids, tournaments etc.