1/2" to 1" poly water pipe is what you need. there's different grades depending on if it's for drinking water.
depth to bury depends on if it freezes where you live. Do you have drains? can you put a drain in?
When I ran water to my garage building, I was the black plastic pipe. Be sure to run the water line 36" or more under the ground. We hired a guy with a trencher. I running up through your garage building concrete floor, use the black plastic tile and run the water line through it. If you ever need to replace the water line, it can be done this way.