If the engine will crank over and start by bypassing the relay, the battery and it's connections are good enough. If the engine will crank and start by running a temporary hot wire to the solenoid connection on the relay, the relay and it's wiring to the starter are good enough. Try those tests first and let us know what the results are. Make sure you have the car in park/neutral with the E-brake firmly applied and/or wheels chocked, as some of these tests also bypass the neutral safety switch and allow the car to start in any gear.