Please don't give up so easily. Building and troubleshooting PCs is a very rewarding experience. It just takes some time and patience.
Plus, a 'professional' at a store won't put half as much care and effort as you would into your build. Sure, he'll plug everything into the right places, but he won't give a frak about cable management or a 'clean' build.
Take everything apart again, watch some videos on youtube
like this one:
https://www.youtube.com/watch?v=ea_bs5G1yYU,
take a deep breath and then start over. When your rig finally comes to life and posts, you'll be the happiest man on the planet.