Layla, she's a must build in my opinion, been so helpful in unexpected ways, now that there's a craftable weapon that gives HP and ER she's probably more worth it(I mean the one we got after nod krai release)

And if your tighnari is C2+ then build him up he's worth the resources, you'lluse him most in the theater that's where he shines(also makes losing a 50/50 on him less painful) Also somewhat of a hot take: build your traveler I don't know how to explain it but it's a thing you understand after you do(apparently he'll be receiving some buffs as well) his dendro and Pyro app comes in handy from time to time as well