I am 25, make 43k a year, and I need help building credit!

In October I started the job I have wanted and that was to become a Software dev. I am self taught, so I do not have much debt.

I am making about 43k a year, and I have 4k left of debt(down from 7k) from some dumb decisions I made a few years back, it is all defaulted.

My credit scored is in the low 500s and my wife and I want to buy a house early next year. While her credit is awesome, she does not make enough to qualify for a home loan herself.

We decided that we do not want to get a credit card, because of... those past dumb decisions I spoke of. What are some other options to build my credit quicker? We talked about an auto loan because she will need a car soon, but I am worried that my debt to income would be to high for us to get a home loan next year.

Any advice?