If you're just starting out and have no or bad credit a secured credit card is the way to go. You give a bank $500 and you use the card with a $500 limit. After a year you get your money back and have an regular credit card.
1) Gray would be a good addition.
2) I don't think it's an always or never thing. It depends on the length of the shirt and the look you're going for.
3) I don't think black shoes go well with chinos or denim and OCBDs.