Buying print effectively takes years to be honest. Print is a wide spectrum, from a little business card to the hand-bound brochure. Clients rely on your expertise to help them get the best possible job for the best possible price. You have a whole lot of learning to do.
To start with, get to know your paper types and weights. Gloss is the cheapest, silk second, uncoated will give you a nice tactile finish, but images will be darker and the job will take longer to dry.