Definitely a desktop build! You aren't going to get a decent laptop for $500, but you might be able to get a desktop up and running. And of course, upgrade it over time.
I don't think this will fit in $500 for a full build, but Core i5 6500 and AMD RX 470 are the best value for money in terms of CPU and GPU.
Thanks for letting me know some cheaper entry level parts sir!
I think I'm leaning towards desktop as well.. More possibilities!