Is there a perfect amount of coins to stake for any specific coin?
So long as your coins are not that few(or above 100 depending on the coin you are staking), any amount above 5$(in current value) would do. i've heard some people say that there is a disadvantage to holding a large amount of coins in one wallet instead of holding many wallet with moderate amounts of coins.
They are right since holding a lot of coins in one coin is riskier than holding it in many wallets with moderate amount of coins. There is a chance that you will gain profit better when holding it in many wallets and it is very likely for you to lose your money when the coin you heavily invested into dumped a lot(when you are bagholding a lot of coins without investing on others).