The very best is stranded, pre-tinned copper wire. I usually buy mine from Jamestown Distributors or West's Marine. But there are other sources also. NOT cheap, but well worth the price in peace of mind and trouble free boating. Like all projects, it better you do it the first time, the longer it will last.
The only brand I have ever used is Anchor. That's what is at West Marine and every other marine store near me. I guess there are other brands but I haven't seen them.
Never bought wire on eBay in the past but I have been using it and Amazon more lately.