just research and build it yourself. 900 dollar self built could get you ~1500 pre built.
Its really not that hard

They both have their ups and downs. Tiger Direct has more options for specialty rigs, Newegg has more sales/specials.

I've tried both tigerdirect and newegg. Haven't used tigerdirect in the last 10 years, so my info may be out of date, but I go with newegg.

Also Google pick my pc parts. That's a good site similar to the one listed above. Just easier to remember.

I would buy a midsized case so you don't have cable length issues. Get a 2nd Gen mobo from asus that suports the I7 intel processors. . A 2 tb hdd(hold out to upgrade to a ssd until you have some cash free up, then put your OS and your fav game on it). The rest of the parts you can fill up with whatever just to get you off the ground. Upgrade it later as your needs increase. The good mobo is what's important.

Good luck.