For trading on IDEX, I will give you some ideas of mine:
BPT - Blockport, marketcap $5.2M
ELIX - Elixir, marketcap $2.7M
CARD - Cardstack, marketcap ??
or if you want a well established project then
IOST - The Internet of Services, marketcap $145M
The most important factor when it comes about what you want to trade in an exchange especially if you're talking about a decentralized one are not the market caps but the volume of the coin, there is no point in buying a lot of coins when there is no volume, you are going to just lose your money if you try to sell them or you are going to become a bag holder.