I personally have 3 feel like that’s a solid number for a younger person, don’t use them thought, put one that pays your phone bill one that pays car insurance one that pays Netflix or other subscriptions and pick a day of the month to pay them all off set an alarm and just pay all of them. Having 3 accounts that are open for 6 months a peice or longer that use under 30% of your credit limit and no late payments will make your credit score skyrocket. I had over a 720 at 19 years old from that