The best answer would be Adobe Premier Pro -

The entire suite costs about $70 per month, which will include photoshop, illustrator, audition and a few others. But all of these will come in handy as you become more proficient. The thing is every software program is different. So, for example if you start on a different one now, and use it for a year or 2, then feel like you are ready to move to something more advanced, you will be basically starting from complete scratch. Even simple things that you thought you knew well, will be completely different. Now the thing with adobe premier is that it can be very complicated - there are so many things that software can do. However, at the same time you don't have to use any of those options, so you can start and keep it simple for yourself. The other benefit of adobe premier, is that it is one of the most popular and widely used programs for editing. So there is plenty of information how to use it. Even to this day after working on it for a few years, anytime i need to figure out how to do something, i just type it into youtube, and watch a 2 minute video on how to do it. As time goes on you start remembering all these skills that you use constantly and without even trying - with just time, you become proficient in the best program there is. Most of the other software doesn't even compare in terms of abilities, but also when you get stuck, you are going to have a hard time finding a video that will solve it for you.

Best of luck - Creating Youtube videos can be a lot of fun, and really profitable if done right.