In my opinion, I believe it is. It establishes credit, and the best use of it would be to charge small amounts, not utilizing a lot of the credit limit, and pay the balance in full each month.
Paying the "last statement balance" in full means you don't pay finance charges. Continual use shows responsibility in using the card and on time payments boosts your credit worthiness and avoids negative reports and avoids all late charges etc.
I don't know the magic number, but you don't want to charge probably more than 10 - 15% of the credit limit.
NEVER charge more than what you can pay off in full OR you have a plan to pay it off a few payments.
Always pay more than the minimum amount. If you don't, it will take forever to pay the balance and you'll end up paying as much or more in finance charges than the original balance!
Yes absolutely. To build card one credit card is enough. To build a faster credit you have to make sure you follow the below steps
It is my understanding that being an authorized user on a credit card does NOT build credit for the user. Only the person(s) who have the account and are responsible for paying the account has the activity reported on their credit. I could be wrong, but that is my understanding from past experience.