It really depends. You have three simplified scenarios

1) the coin starts going up and you buy as it goes up and it keeps going up
2) the coin starts going up and you buy as it goes up and levels out
3 "" it goes down soon after you buy

Obviously #1 the question becomes how long do you wait before selling. This should be based off what you know about the coin and why the coin is rising.

#2 the question is do you hold hoping for another rise or sell. There's opportunity costs in holding while others go up and potentially same costs in getting out too quick.

#3 depends on if you believe in the coin or were just trying to catch a train.

A simple solution would be to use stop losses soon after you buy to ensure that you only get #1 & #2.

It gets complicated with what if scenarios from there but maybe that helps