You should start off with looking at different components you are going to need for the type of work you will be doing on your pc-the motherboard, hard drive, video card, fans, cases etc. New Egg has a good video to get you started.
There is also a guy on YouTube who works in a Canadian electronic store called NCIX. He has a lot of I formative videos. The channel is called NCIXcom, he has a few good build guides.
$500 should work for you unless you plan on going for the latest and greatest. Subscribe to Newegg's newsletter as they always have deals on anything you may need. Thats how I got most of my parts.