I have a shed 14x28 feet. How much can I grow and what do I need? I want a huge harvest lol
Try starting with a little reading. Download the Marijuana Grow Bible
The amount you will yeild per square foot is very dependent on “grower’s talent”. Training and pruning will get you your biggest yields, i.e. topping, FIMing, ScrOGing or SOGing. A good light system is important, with HID lights and high quality LEDs being the most effective and efficient. Fluorescent light can work but usually yeild less as they just don’t have the penetration that high pressure sodium, metal halide, or high output LEDs have.
Check out thus chart for an idea of start up costs as well as long term costs associated with the various types of lighting available:
Check out this link as well where we discussed some similar ideas. You will likely want to divide the room into two or three sections depending on the style of grow you decide on. For a perpetual grow, you are going to want at least two rooms, a smaller “grow/veg” room and a larger “bloom/flowering” room. Some run the nursery/propagation in the veg room, but others divide the space further to have a very very small section for the nursery/propagation. The general idea is to have the smaller plant or plants in the veg room just getting ready to be put in the flower room right when the plant or plants are ready to come down from the flower room.
http://www.ilovegrowingmarijuana.com/community/topic/marijuana-grow-shed/#post-19998
Growing Marijuana in order to get a huge harvest is a lot of work and time consuming. I wish you luck and hope you have a good grow. 
Let us know if we can help.