There are a lot of coins that are on the exchanges that still ahve the potential for 10-100x. even on Bittrex you have them. They are the ones with lwoer volume and small marketcaps. But there is a reason for why those coins haven't taken off:
- Either the technology isn't that great and it doesn't have the real life adoption that it needs
- The coin is still unknown or the technology potential unclear
It is the second typ of coin you want to find. The only way to do that is to do your research on the coins you find interesting to by yourself determine if the coin has potential and possible adoption before everyone else.
Even smaller coins normally isn't on Bittrex but can be found on EtherDelta, Cryptopia, Binance etc... Since not as much trading is going on at these exchanges there are many coins that haven't yet taken off on them
Another way is to be here at BitCoinTalk and read ANN threads on ALT Coins