That would depend on your preferences. Whether for a short term investment of for a long term. Perhaps dependent on your usage as well. Will you use it for a macro transactions or for micro. There are many factors to consider but I'll assume that you are up to the profits so selecting the existing strong coins will be the best option. BTC, BCH, ETH, XRP, IOT would be in my preference but if you want some new coins/tokens out there, consider TPAY (not yet tradeable) , XUC, POS.