Earrings should look conservative. If you don't own a suit, borrow one from a friend or consider investing in a high quality one. A tailored suit will last many years into your professional career. If you are unable to obtain a suit, a conservative sports coat and dress slacks are second best. White shirts are always your first choice.
Solid blue is an acceptable alternative.
If you don't own either a white or blue shirt, go out and buy some. There is no short cut here, and if you get the job you will probably need more than one anyway. Stay away from outlandish styles with buckles or chains. Never wear white or tan shoes. Avoid run down heels or holes in the soles.