I'm trying to raise my credit. Will a store credit card help?

Since you're only 18, you only need one credit card for the time being. The balance should always be paid the following month but since they are not charging you interest, it'll do for now. Once you're employed 12/18 months and have $500 in a savings account, you should get a secured credit card from a bank. Make sure they belong to the credit bureau. After 24 months of activity with both cards, your credit score should be between 660/749 which is a good score. This will give you a lower rate on loans and when you apply for a mortgage.