Even though I don't deal much with altcoins, still I have a way to check the best performing coins just to keep track of the market. There is a easy way to check that.

Visit coinmarketcap website. Then click on the "Change (24 h)" tab. It will sort the entire list of coins on the basis of price change in last 24 hours. Click it twice, it will sort the list as per the least moving coins. This way you can find the most precious coin's list as well as the least precious coin's list. Click on the market cap and the list will sorted as per the highest market cap list. Very similar to the filter function of excel.