@LerX
i5-2400 and 8gb of ram... that's a decent budget rig. You just need a good gpu, and that pc will handle many games comfortably at 720p, and some would even run well at 1080p.
we go back again to the important issue of power supply. Psu's no matter how good will all die with age, simply means an aged psu would be supplying less than the wattage advertised on it.
if you can't change the power supply. I suggest going for gpu that don't need external power like GT 1030 (GDDR5), GTX 1050ti, or a GTX 1650. These are still so much better than your GTX 650.
here's a video on what a GT 1030 (GDDR5) can do. GDDR5 version vs. DDR4 version. PUBG, Overwatch, Fortnite, and Rocket League.
View: https://youtu.be/a80mtoQklSo