Should i major in finance, marketing, management, double major, etc

I have had one credit so far but my payments were not kept on this one card. So i have made my decision and that is to not apply for another one. What are some ways for me to build my credit without credit cards. I have my own apartment and my cell phone wit tmobile.
where are some places that i can apply for a car loan?

i want to know how much should i spend on each credit and should i pay off completly or should i leave a few dollars on i heard that you should use 30% on each then pay off each month but leave 5 10 dollars so credit card company get some money . also will it hurt my score if i don’t use my 5 cards monthly? I only use my cards for bill, gas groceries ect. so i know i’m spending money that i already have. does any one know what are other things i can do to bring up my credit score. i have a 580 right now but i will be looking to get a house in a year or two so please if anyone has any ideas on raising my credit score pease respond thank you.

My sister and her husband just found out they’re pregnant, and now her husband is researching life insurance. Which is best for a new family? They make average income for a couple.