I have always used power wires from my days of screwing around with car audio. It's very fine, flexible, and often tinned OFC.

Check out Knukonceptz.com, they sell by the foot, many car audio shops do as well. They have 8 AWG for 25c a foot.

I buy most terminals from eBay, as they are quite expensive locally.

Jumper cables work but I've often found the cable to be pretty lackluster.