PC Upgrade Help

Hi I am relatively new and clueless on how to upgrade my PC. I had bought this PC 3 years ago now for a decent price, the seller said that all it needed was a better GPU and then it’d be great. I’ve only really played league on it so there wasn’t really a rush to upgrade, but now I want to play more demanding games. I have no idea where to start and what to look for so I wondering if anyone had any input or recommendations on what I could possibly get to upgrade. I know that I definitely need a better gpu but do I also need a better cpu as well??

Here’s what I have on my PC at the moment. Thanks!