Don't bid on anything yet. Although common ones can be had for not much more than melt value, there are lots of fakes and ways for beginners to get burned.
First step would be to research in advance what you are interested in. CCF has a big collection of 8 Reales aficionados and experts. Probably 20-50% of the posts on the world coins subforum
is about 8 reales coins. Spend some time reading the posts by swamperbob, jfransch, mathieuma, twokopiecki, etc... They are a friendly bunch and welcoming to newbies. . .