Your situation isn’t clearly defined. You indicate that you have a credit card, for what reason would you want another? You seem like a “credit seeker”. This is someone who becomes obsessed with getting new or more credit on a continuous or routine basis. The banks often view this in a dim light, essentially shying away to avoid adverse selection.

Account history for a minimum of 2 years is ideal. More if you can.
You have too many new accounts in less than a year. So you’re applying for credit too quickly. Just wait a year or 2 more.

It usually takes about 12 months The best way to increase your credit is to get a small loan for 24 months and pay it back in 12.

It’s a combination of things.

Normally lenders look for 3 years in the bureaus with 4 trade lines paid as agreed and at least 1 installment loan paid as agreed for at least 12 months.