The graphics card is the most important thing. Basically look for a gaming pc. I’m not current on the Radeon number system, but for Nvidea cards you want a 3 number card and generally the last 2 numbers should be 60 or higher. The 750Ti is an exception to that and is a relatively inexpensive card that can run UE4. You also would have better experience with 8 gig ram, though I think it will technically run with 4. Quad core cpu.