Need help building first gaming PC budget $600-$750

Hey I've been a console gamer for years, but now i have decided to move onto pc gaming ,since I would be making a new pc i have no idea what parts to buy, and your help would be appreciated, if i can't afford what i want for the price i might be able to entend my budget a little
Details:
Using my 1080p LED 32" HDTV
Budget $600-$750
Parts i already have. Operating system, mouse ,keyboard
Some specs i require 8GB Ram, Disc drive, 500gb HDD that's fast and efficient, upgradeable, video card with hdmi input
Want to be able to play modern games for years to come, maybe like 3 or 4 without needing to upgrade
And i apoligize if this is in the wrong section
I also don't plan to overclock