To build credit with your credit card you should use your credit card at least once or twice per month and then pay the credit card back.
However to keep your credit card account active you should use the credit card at least every 3 months to 6 months.
In general, you should plan to use your credit card every six months.
However, if you want to be extra safe, aim for every three.
Some credit card issuers will explicitly state in the credit card agreement what length of time is considered to be inactive.
Too many credit cards won't hurt your credit as long as you use the credit cards responsibly.
However if you use too many credit cards and don't pay them back then they could hurt your credit score.
There's not really such a thing has having too many credit cards.
However you could have too many credit cards that you cannot pay off which can hurt your credit.
Generally it's a good idea to only have 3 credit cards and use them responsibly and pay them off on time to help build your credit.
If you have more credit cards and use them without being able pay them off then that can lower your credit score.
Having accounts open with a credit card company will not hurt your credit score, but having zero balances will not prove to lenders that you are creditworthy and will repay a loan.
Lenders want to make sure you repay, and that you will also pay interest.
There is no ideal number of credit cards you can own.
You can own as many credit cards as you want as long as you are eligible for it.
However, having multiple line of credit can make you look like a desperate borrower and increases the overall available credit.