I think you should do what you can with it as is. Free parts are fine but limit your spending on the bike. It will be a good project and will increase your skills as a mechanic. Swap of parts from your parts of used bikes as parts break on your current bike. Get as much as you can out of it. Try reducing air pressure in the front for better traction. Post online craigslist that you are looking for some free tires and parts explain your situation.