If you are trying to by altcoins I'll advice that you stick to coins listed in the top 100 on coinmarketcap.com to avoid entirely shitty coins, ETH, BAT and Doge are good options you should check out.
There are coins that are below 100, yet they do brilliantly well. Some of the coins in top 100 still fall below. Therefore, going by the position of coins, I will recommend choosing from either the to 10 or the top 20. At least, that will put you on a safer side.