Serious credit card put somebody through the mill!!? I am 21 years old, 3rd yr of college, remunerated every year

I am 21 years old, 3rd yr of college, remunerated every year by myself with my own brass, work FT/school FT. I did have to find a small $5,000 school loan wh/I reimburse on monthly of $100. That is the only debt I own & the only item linked to my credit. I pay cheque cash for everything I buy, if I can't afford it, I don't buy. Because of this I hold an excellent credit score of 712, but beside a short history. My mom & b/f said I should think of getting a credit card and buy my gas next to it (I only pack up twice a month at $45 each time) & take-home pay it off monthly only to establish more credit & to add length to my credit history. I also own thought of getting one in extra to that idea to use within an emergency ONLY! Would these be legitimate reason to get one and should I return with one? And which one? Reward card, cash hindmost card? Personal/student card? And which provider: chase, citi, capital 1, well fargo, bank of america? I want low interest, no annual tax, & only use it for gas & emergency.

Pick one next to no annual fees. The other stuff doesn't much matter.
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