What would be unreal 4 performance in my this specs

I am thinking about building a custom pc for unreal engine… Im on a medium budget…

Gpu: asus gtx 750 DF 2GBD5
Cpu: AMD FX-4300
Motherboard: Asus H61M-k
Ram: corsair vengeance lpx 8GB DDR4 2400Mhz= 8gb x 2 = 16GB

It’ll run. That 16gb is good idea, the FX-4300 should be adequate. I’d try to squeeze as much GPU out of your budget as you can.

I currently run an AMD FX-6300, 16gb RAM, and an R9 290 most of them time I get pretty decent frame rates, unless I try something like too many dynamic speed trees and grass everywhere.
I used to run on an Radeon HD 7790, the upgrade to the R9 290 was really great, and I haven’t had any problems since.

I’ve run UE4 on an Athlon II X2, with 8gb, and my old 7790. I was able to get something done, but, there was pretty much no real-time preview feedback when I was building materials, I had to save and wait to see any changes I’d make.