You wrote: "i need a power supply, case, ram, hard drive, dvd drive (I have an ss drive already) cpu and motherboard"
If you need all that, you're going to need to buy used and you're probably also going to have to buy a complete system. I can't imagine buying all those parts - even used - and stay under $350. However, there are plenty of used systems available on eBay for less than $350 if you're willing to go Core 2 Duo. I just looked and you can buy a complete, working, system for under $150. You'd need to add more RAM but you will have plenty of money left over to buy that. I also looked at intel i3 systems and it appears that you'll spend around $300 just for a case, power supply, motherboard and CPU. Leaving a DVD drive, HD, and RAM. That would be way over budget. Maybe some searching will find better deals but I doubt you'll stay under $350 for everything that's needed.
If you decide to buy an older core 2 duo system make sure the motherboard will accept 8 gig of RAM.