7k is a good price for than much square footage. For that building it’s going to be delivered completely built. As for the base getting it level will be first priority. Depth is not as imperative. Ideally you wanna start at the high side of your spot dig down three to four inches and fill back up flush with grade. Then from there set to whatever it takes to make it level. In addition run a foot larger than the building all the way around. In your case this will be 12x22. By doing this your gonna make a drip line around the building. It will also allow for some wiggle room to get the building at just the right angle. One last tip if your delivery is after the first snowfall tarp the site before the snow if you have ever tried to shovel crushed stone you will know why.