Go W build almost every game, it’s her best build.
Hot Pursuit, Punishment, Arsenal, Rain of Vengeance, Gloom, Frost Shot, Farfight Quiver.
For BoE (race) and some special occasions (like when you want to force camps/bosses all the time), you can go Q build.
Monster Hunter, Puncturing Arrow, Repeating Arrow, Rain of Vengeance, Gloom (Siohoning Arrow can be good but usually Gloom is just straight up better), Frost Shot (control of the fight with the slow) or Seething Hatred (makes your Q do more damage), Farfight Quiver.
Honorable Mentions:
Level 7 Death Dealer. This can be a fun talent and can lead to some really sick plays, but it’s a little bit harder to use and usually if you don’t get the E reset you end up in a bad position.
Level 10 Strafe. Rain is better for 90% of the games, but this one can be good if you lack damage really (but then if you lack damage you failed draft/Just a QM thing).
Level 16 Manticore. Just a pretty good % damage talent. Take this if you need to kill frontline.
You should never go the rest of the talents that I didn’t mention here. They are just bad talents or just worse than the others so it’s not worth picking.
Extra tips:
If you got a true Valla comp (double support), you just want to be as aggressive as possible with her and try to force fights. Your strenght is team fighting, so try to go for it (don’t forget to also soak though).
Just keep pressuring the frontline with your AAs. That’s the best thing you can do. You are not a dive hero, so don’t dive.