I wouldn't start of straight on building your own without any experience. Rather take your money to any computer shop and tall them what you're looking for.
I seriously recommend going for an Intel/Nvidia build (Get at least an Intel i5 CPU/Nvidia 600 series GPU).
But from there it will be up to you to upgrade and maintain your desktop. That's how you'll learn and eventually maybe even build your own desktop from scratch.
Good luck dude.