If the engine sounds like its “trying” to start (as some say) - strongly going RR-RR-RR-RR-RR then skip the starter, battery, flywheel, etc. They are doing their job.
Use a spark tester or spare plug (any auto parts store) and find out if there is spark. If not, troubleshoot spark.
Spray some starting fluid (any auto parts store) into the intake and if that gets it to run, even if for a few seconds, then you troubleshoot fuel. It does have gasoline in it doesn’t it?