Your platform, FM2, has no worthwhile CPU upgrade past what you have now. Those APUs were not meant for gaming. With your current system the most you could do is increase your ram to 8gb and add a better videocard. The problem is these upgrades would only help performance in games that run fine on your A8 but need more ram and more videocard power. PUBG is not one of these kinds of games.
If you're looking for better PUBG performance you will need a new CPU, which means a new motherboard as well, and if you building a new system that means DDR4 ram as well.
You could switch from AMD to Intel and buy an older pre-built with an i5 2400 or something like that in it. However, with PUBG that RX 460 would then limit your performance. So be aware of that. PUBG requires a lot of CPU and videocard resources. I know, it sucks, but PUBG is one game that is tough for budget PC gamers to try to play.