For fast action shooters, adding a GTX1050ti would be good.
It is not clear exactly what cpu you now have; I can find no A4 5400 processors.
CPU-Z will tell you exactly.
Unfortunately, all a4/a6/a10 processors have slow core speeds that games such as Dota2 require.
processor has relatively slow core performance.
and, there are no good upgrades that will fit on your motherboard.
To see if a better graphics card will help, run this test:
Run YOUR games, but lower your resolution and eye candy.
If your FPS increases, it indicates that your cpu is strong enough to drive a better graphics configuration.
If your FPS stays the same, you are likely more cpu limited.
If you need to upgrade to a better cpu, you are looking at 8/9th gen intel or ryzen. $200 will buy you a intel G5400, motherboard, and 8gb of ddr4 ram that will do better than what you have.
It will be upgradeable.