Any given motherboard will have some listing of the supported components: CPU, RAM are especially important.
There are likely to be several workable combinations you can use for a gaming PC.
Use the system in the pcpartpicker link as a guide. Or the Tom's Hardware build that is within your budget.
Pretend that build is your gaming system. Then look at one of the games you desire to play.
For example GTA v. The build includes 16GB (Kit 2x8GB) of memory. How much memory is recommended for GTA v?
Check off whether the build meets the gaming requirements game by game. If all are met then that is the system put together.
If not, vary the build to improve where the build is weak and go through the process again.
Only you can make the final decisions between price, performance, quality.