It might be worth you popping over to the buildapc subreddit, lots of good info over there and people will be able to suggest particular parts to fit within your budget. Looking at this you'll be wanting a new CPU, which necessitates a new motherboard. You can stick with the same power supply and graphics card. Your RAM could be upgraded (recommended if you go with a Ryzen CPU), but you can stick with it for now if budget is an issue.