1 gigs per second
Quit using the magic number bank. No hard drive reads 1GB/s. SSD's struggle to get above 500MB/s.

http://www.newegg.com/Product/ComboBundleDetails.aspx?ItemList=Combo.1644347
AMD is the budget king. The 4300 is decent for standard applications, but don't expect it to preform as well as a 8350 octo core. I wouldn't go with that because it has a single stick of RAM. Dual channel ram is better, as there is twice the communication between your CPU and RAM. You also said you had an old PSU, but the one that comes with that bundle would probably be better anyway. That's a decent mother board, has sata 6 for an SSD like you were talking about. That hard drive looks good, but personally i would go with a 64mb cache for better performance. Don't count on your dad's friend coming through with any kind of nice GPU, they're expensive and I can't imagine why they would be giving them out.
http://pcpartpicker.com/p/3KXxjThat's as close to $500 as I can get. With a low budget PC, you're going to take performance hits on your video more than anything, but I tried to spread it out across all the parts. If you wan't to include a monitor, keyboard and mouse, go with the build below. It's a lower power APU, but it can still handle Blockland and regular work.
http://pcpartpicker.com/p/3KXFBYou could cheap out on the monitor, keyboard and mouse, but you use those every single day, would you really be satisfied with sub par performance?
Remember, these lists's are just guidelines. In the end, you can add/remove whatever you want.