Replying to Upgrading a shitty computer

I have this idea, to take a cheap computer from my dads office, like a rather modern dell. A dual core pentium anniversary editon. No graphics card. but its free. My idea is to overclock the processor, slap a dimm of ddr3 and run it in dual channel. Take the os and put it on an ssd and use the existing hard drive for storage.

but my question is, is there a solid graphics card that doesnt need external pcie power?

and have any of you tried doing this?