One of the best places to find gems and do trading without too much volatility is Cryptopia.
In my opinion Bismuth is gem, cause it's not yet on other exchanges, and it's pretty stable and easy to trade.
So best tactics would be to trade gems like that, accumulate more, it get's listed on other exchanges and you earn big.
Disclaimer: I'm not associated with Bismuth's or Cryptopia teams but hold their coins. This is not financial advice, just my personal opinion.
This method isnt really a gem but do have the possibility on making some profits but still it would be entirely depending on the progress of the coin.If its just listed on a single exchange it doesnt mean it would be worth to accumulate if you dont base into other indications like project updates, active devs and etc..If you do see these factors then it would be worth to try or put some risk but dont expect anytime that the same scenarios would happen.