Question about credit cards

Hey guys
I have a quick question regarding credit and credit cards. I have 1 secured credit card ($300 limit) with Capital One and a $12,000 car loan with Santander. I haven't made any late payments yet (I've had a credit score for 2 months). My credit utilization (according to credit karma) is 33%. I was talking to my girlfriend's parents, who have insane credit, and they gave me the advice to never use a debit card again. Only use your credit card, then pay off the balance. Problem is, my limit is tiny on my current card and it won't get increased for a while because it's a secured card. My girlfriend signed up for a student card (no security deposit) with Discover and got a limit of $1,000. Her score right now is about 670 where mine is 644. I was doing some googling and some places recommend you have multiple credit cards, so do you think I should get a student Discover card too? I hit a bad financial spot a week or two ago and almost maxed out my Capital One card (though I don't owe anything for almost a month now so I'll pay off the balance when I get paid in a week). Is it smart to get that second or a third card?

Thanks

Obviously the most important part of a credit report is timely payments. But almost just as important is percentage of credit utilization. So, the more credit you have, the lower the utilization. (assuming you don’t max everything out).

The short term problem is that new credit temporally impacts your score negatively. But that is short lived. For now get all the credit you can, but control the use. Do try to keep the utilization low every month. They are correct, use the credit, not the debit, but make sure you pay it off fast.

Eventually they will start sending pre-approved cards and increasing the limits on the ones you have. BUT, do not take the ones with annual fees!

I have excellent payments but my score can jump by 100 points either way depending on my balances. Originally I just wanted enough credit to cover what I needed. That caused high utilization. I then got extra credit that I didn’t need or use just to decrease the utilization percentage. Made a big difference in the score.