Alhaitham is largely complete at c0 which is nice. His cons are okay but you don't get a big bump in damage from c1 or c2 like a lot of over five stars. He's my main DPS since he dropped and while theres a bit of a learning curve, I enjoy his gameplay.
Alternate pulls between Kazuha and Alhaitham until you get one, then save the rest. Alternately, do that on a wish simulator and measure your reaction after you get one of them, then use that to determine which one you want. Unless they do another archon stack like they did in 3.1, you should be able to save enough for all three.