How do I best tear down a small building?
OH, looks like fun!  Love to demo small buildings.   Basic tools will be great. Large rip claw hammers, pry bars, a good 4 foot demo bar,  a circular saw, and MOST IMPORTANT tool would be a good reciprocating saw with long bi-metal demo blades.

Be careful, start at the top, remove the roof panels. cut off the rafters one at a time. then either cut and knock down the walls and dismember, or take off the sheathing first, then disassemble or cut off the framing.

Wear good gloves, boots, and eye protection.  I dumpster is a good idea also.