I am not a USAA Advisor, nor a USAA Employee. I am just a Member like you.
That said, the subject of Improving Your Credit Score is too complex to give you a simple answer. This forum has Moderators whom are Financial Advisors whom may be better able to answer some your questions.
A key bit of advice that I can give you is that you should not start any "plan" to Improving Your Credit Score without talking to a financial advisor first.
Also the only real help I have for you are the following LINKS which should answer some of your questions.
1. USAA - Financial Advice Blog (maybe you could post a budget related question there)
4. MyFICO - About Your Credit Score **(External Link)
I hope I have helped you.