Fuel or spark. Get a can of starting fluid. Take the top off the air cleaner and spray some of the fluid in while someone tries to start it, keep head back in case it backfires. If it starts and runs on the start fluid it's a fuel problem. If not it's ignition related. If the clutch is bad the engine will run, but slip when trying to go. Worse slippage in 4th or 5th gear than first, and usually it will be hard to shift.