Answering questions about what is the the best software for postproduction is a bit like asking what's the best camera... It really depends on what the context is.
Most features and TV use avid media composer which is expensive and fussy but has a bunch of collaborative editing features that mean if you're in a big team it has some decent benefits (especially if you have avid servers and a lot of big post houses do). If you are using avid's codecs it's also very stable on huge projects. If you want to work in a big post house it's definitely useful to know. Otherwise, for small and low budget stuff it's probably unnecessary 98% of the time.
Premiere is where I would probably recommend most people who want to get I to editing start out, not least because if you already have Adobe Photoshop and/or Lightroom then buying the rest of the Creative Suite/Cloud is fairly inexpensive. It's a lot easier to get to grips with than Avid, but still a very powerful tool, especially when combined with After Effects (the creative cloud compositing and motion graphics program). It's a shame that Adobe seem to be killing off Speedgrade though, which has was their colour grading package, and no longer has a direct link facility from Premiere. The Lumetri panel in premiere has improved, but its not really a like for like replacement.
If you are more interested in grading than editing (and have a powerful enough computer) than Davinci Resolve is worth a look. It's a fantastic grading program with a rapidly improving set of editing tools. It can be a bit fussy with some consumer codecs though. The good news it that the lite version is all you probably need and it's available for free.
There is also final cut pro, which used to be the main alternative to Avid, but in the change from v7 to vX Apple basically left the small and demanding pro market to appeal to prosumers. Its popular with some of the students we get, but I don't know many places that use it professionally.
Below that you have things like iMovie and Windows Movie Maker that I couldn't really tell you anything about beyond that they're designed to make life easy for people with no background in video.
In terms of not wasting money, Resolve is free and Creative Cloud has a free 30 day trial, I'd have a look at both hands on and look at some beginner/interface tutorials to get you started and think about what it's likely to work out best for you and what you want to do with video.
Whatever you decide it won't be like you're stuck in a windowless rooms for weeks at a time editing VHS tapes together, which is how I learned to edit. The tools we have available today for not much money are pretty amazing in comparison.
