Firstly, you have to think to your self exactly what you need to achieve with this software whether it is to composite awesome visual effects into your videos or simply want to cut and edit videos.
I could go on for days but I'll keep it simple...
You have a few options depending on your budget and needs:
Windows Movie Maker
I guess at some point in our lives we've all made a movie on this platform. This is the most basic way to create a video and all you really need is a Windows Computer or Laptop. (It comes pre installed). This will allow you to make very simple edits and composite, the UI is easy to use and beginner friendly.
Price: FREE
iMovie
This is what I recommend to any beginner who wants to get into the videography industry, it will give you the basis of what you need to start making movies right away, has a great UI and easier to use then Movie Maker (In my opinion). It comes with lost of royalty free sounds which may be helpful to tose wanting to start making movies on a budget. The only draw back is you'll need a Mac.
Price: FREE
Sony Vegas
Excellent media sharing and timeline sharing in multi-editor environments. Very established standards, practices and troubleshooting. The best usage I've seen for this is in professional post-houses with a ton of folks working on one show. It may be a bit much for standalone video editing, but if you want to get serious this may be an option. (I personally do not use this anymore)
Price: $700
Final Cut Pro X
I was a massive advocate for FCPX as it was simply the best video editor of it's time, it was simple and easy to use which also incorporating the more advanced features, although over the years Apple has made the software very rigid therefore you have to work for the program and alter your style to suite the programs. For the more professional editors out there this may not be the greatest solution anymore, although for those who want the advanced features along with the great usability, I would recommend this.
Price: $300
Adobe Premier Pro
This is my favourite of all, this is what I currently use and I am loving using it. The program works for you, you don't need to alter your style to work for the program, it simply works. There is a very steep learning curve though jumping from FCPX to this was quite different in terms of the workflow a UI. I would recommend this for the most advanced users out.
Price: 19.99 a month
To answer your question, I would go for iMovie, although if you want to leave your mark with your movies go for Final Cut Pro X. I put the rest in there for others who want to decide on what's best for them. If you want to know anything else about video editing leave me a PM.
I create videos/movies for a living.