Just level up whoever has the highest level cap. Before level 160, Saveas will probably be your best hero. Don't ascend any hero to Legendary unless you have or can guaranteed get more copies to reach L+. This probably means that early on many of your highest ascension heroes will be legendary tier and many ascended tier heroes will be stuck at E+, but that's fine because you can feed L+ junk heroes to non-junk heroes.
Set up your wishlist in the tavern. Walker is the worst ascended hero in the game, and the wishlist would have blocked him.
Light: Rowan, Rosaline, Raine, Hendrik, Gwyneth, Morrow, Cecilia, Estrilda
Mauler: Kren, Tidus, Skriath, Brutus, Skreg, Numisu, Granit?
Wilder: Eironn, Lorsan, Pippa, Lyca, Saurus, Raku, Tasi
Grave: Thoran, Daimon, Grezhul, Silas, Ferael, Oden, Izold
These are ordered by how important I think they are, but I'm not familiar with current early game meta so this advice could be off. I'm confident on the first four in each faction, and the recommendations after that are flexible.>>602086
I disagree with this guy about Shemira. If you're gonna spend lab tokens on an early game carry with a limited late game niche, do Wu Kong. Wu Kong will need 14 copies to reach Ascended compared to Shemira's 8, but Wu Kong won't take L+ fodder away from other grave heroes and is given out frequently. When Evil Nemora is the TR boss, just merc a Shemira. Every longtime player has her.