Should I upgrade or replace my PC?

I have a ASRock B450 ITX Fatality Motherboard, AMD 3400G Cpu, 8Gb x 2 T-Force Xtreem DDR4 4000Mhz Ram and a XPG 240Gb M.2 SSD.

It's in a In-Win Chopin case that has it's own PCU. I mainly used it for Media use. But wanna use a PC now to play games on.

Should I try to upgrade? Or do I need to do a full build?

I just wanna be able to play most games. Nothing flashy.

I figure I would atleast need a New case, PCU and GPU. And maybe a new CPU if need be.

What would you recommend? And what kind of GPU/CPU should I be looking at?

The most demanding games I would want to play would probably be Racing Sims Like the Ride series and MotoGp series. Otherwise, Fighters and Shmups would be my other games.

Tried posting in BuildaPC but all I got was downvoted and only a single reply.