How to Utilize my Computer for Best Gaming Performance (may need new GPU)

[Flashera]

Hello, I would like to know how to gain the optimal performance for games like Total War, or Minecraft with shaders.

Computer:

ASUS CM1745

APU: 3.2 GHZ (AMD 5500 (I think))
Current GPU: AMD Radeon HD 7645
8 GB RAM
350 WATT PSU

 

[Flashera]

Oh by the way, I am only willing to use $150 to upgrades