For buying good links, spend some time on Google finding some good websites/blogs in your niche and get in contact with those website owners or bloggers if they are interested in placing your ads on their websites/blogs for some dollars
DP has a lot of good link sellers. You can try your luck there and look at their reputation for added reference.
We do sell links, but go to buy and sell (link sales). There are many links being sold in that section; you can simply choose and pick what you like.