Try to cut your budget as short as you can to switch that 1050ti for a 1060 3gb at least! 1050ti are not that good and you do get a great boost going with a 1060. Switch that i3 to ryzen 3 and buy a cheap B350 mobo. 60fps in almost all the AAA titles
That's pretty good for 600 usd, don't change the i3 for a ryzen CPU, that i3 beats the shit out of any ryzen 3, maybe change to a 1060 if he wants to play vr in the future.
Build an older standard pc. Like i5 3rd or 4th gen, DDR3 and all that jazz. Then you can spend more on your gpu. Just make sure not to bottle neck and you can have a older PC that performs just as well for a lot less.