Well, anything less than a 1080 Ti and you'll be golden. The 1500X probably wouldn't bottleneck a 1080 Ti too badly, but it is a bit of an imbalanced system from a budget standpoint. I think the most I'd want to put in a system with a 1500X would probably be a 1070. The 1070 would be a good fit as you'd get the full performance, and not break the bank.
Looking at the GTX 1050, you are going to get all the GPU has to give, but you'll have a lot of CPU resources left over in most cases. Not a bad thing, but you could easily got for something like a 1060 or 1070 if you had the budget.