It would entirely depend on the coin you are investing into. 3% stoploss maybe good to avoid excess loss but there would actually not be that need to set a stop-profit. Even if your coin crosses 10% profit, than even you can hold that coin by setting up a new stop-loss which will never make you have loss instead of profits.

This would be a good strategy for making profits rather than loss but you should be cautious each time to avoid losing more than you could win. Also each time try to buy at a dip which would give you major chances of reaching your expected price and it would rather be much profitable for you.