I think you can consider to buy a wave, which is a more valuable COINS, you can went up from its technology research, as well as its white paper, and the process of the project, the market value of the relative wave currency now or is lower, so if you want to do double or turned over several times, is also relatively easy to do, and eth will be relatively more difficult, of course, the eth is a very worth money, above is my personal advice, you have a good grasp!