don't mine anything unless it hasn't had an ico yet.
and really, probably just don't mine period. it's not worth it anymore unless you already have some extra income.
just do research on coins before they go on an exchange, or try to be a part of the ico.
buying coins that are already listed is riskier because of how many worthless coins there are that are going nowhere.
just research them a lot before buying and holding. there are useful subreddits for this.