Well This is a good math problem, and it will be you that has to work it out. Drawing up plans, and calculating materials is part of life, and you will find that if you draw the plans out, and do the math, life will get easier and cheaper too, since others will not be easily able to overcharge you.
I'll help you get started. To help you decide whether you can afford what you want or not, start with what you think you want and do a guestimate.
If it is a frame that is wire covered, you can put them 4' or 5' apart depending on the width of the wire.
If it is a building you can usually get away with 24 inches from center to center.
Plywood, siding, etc. comes in 4'x8' (4 foot by eight foot) sheets, so if your dimensions are multiples of that it is easier and you save on materials. So 10x16 isn't likely to cost much more than 10x15.