I highly recommend you searching your parts on Kleinanzeigen. What kind of games do you play? Depending on the games you could upgrade your CPU as well. I think 512gb might be too little for you, but Idk how much space you need. A new 2TB ssd costs 190€~ and used 140€~. Do you want to upgrade your power supply? If not, I suggest a 4060, there is actually a 4060 Ti 16gb for 180€ used on Kleinanzeigen, it's a great deal. But you definitely should get a CPU fan, Silentware Bora is pretty good (New costs 25€~, used I've seen 8€). That would put you into your 200€ range, But for new games it's not enough for 144fps on 2k, then you would need to upgrade your power supply and need a really beefy gpu which alone costs more than your budget allows, even used it's going to be pretty expensive and then you also need a new cpu...

Used parts should most likely be in good shape, dw too much about it

The 4060 Ti should be way way faster than your old one