I have whatever the newest version of iMovie is and its actually really good, super easy to use and you can even do basic colour correcting like exposure, contrast, tints. I barely edit, I usually film a second angel and toss the clips to friends so its fine for me.
Do what you can in iMovie, if it does the job, you will end up saving tons of money! If you need to do more, I would go to FCPX. For the money, it is pretty good and will be really easy to use so you don't have to watch hundreds of youtube tutorials!