what game do you intent to play? amd FX series era just ended, so its no point to upgrade the cpu since amd ryzen are far (by lot) better.
Now that cpu is out of the way, the rest are SSD, gpu and ram.
If your ram is 8Gb, then its still good as upgrading it will only waste money.
If you still using HDD, then SSD is the best option. The descent 480/500 Gb SSD should cost around $120. Once using SSD, you would feel fooled all these years for not using it from the beginning. Once tried SSD, you will never want to look back.
Your GTX 950 is not that bad of a gpu. If you willing to upgrade, then I would suggest no more than $200 amd RX-580 4Gb as your cpu will bottleneck any card above it. Make sure your psu is able to keep up.
Good luck