If you are willing to upgrade your platform in the short to mid term ie; 6 months I would recommend buying the best possible graphics card your budget allows, depending on your PSU of course. Then upgrading your Platform. I would even suggest upgrading to a cheap AM4 based system with DDR4 (now quite cheap).
If you aren't intending on overclocking and have a limited budget, wanting simply an updated PC with all round better performance then
the Ryzen 5 2400G with the vega 11 APU ( integrated graphics ) could be a good option if you have modest gaming needs.
1st gen Ryzens are also starting to sell very cheap on the used and new markets.
Ask yourself these important questions as others have stated.
- What is your budget?
- Are you looking at the best gaming performance or all round performance?
- What is your current PSU?
- What games do you want to play?
- Are you just looking for better performance within the scope of games and applications you use currently?