On Linux, Kdenlive is like Windows Movie Maker on steroids.
You'll want to save often, it can be buggy, but once you learn how to use it, extremely powerful. Basically exports into pretty much any video codec format imagineable.
For animation, you'll want Synfig. Again, buggy, but it's the only decent ragdoll/bones based 2D animation tool out there that's reasonably easy to pick-up (but when exporting, save yourself the hassle: replace .gif with .avi, it handles it just fine).
For static images, use GIMP.
It's worth bearing in mind that your video development style will improve over time. Your first few videos are likely to be pretty shit in style, but by every tenth video, you should find notable improvements.
I went from static images akin to a slideshow to greenscreening 2D animation ragdolls.
For audio editing, you'll want audacity (it's as simple as it gets).
Poorfags can bypass the hassle of generating audio files or splashing mad cash on high-quality mic setups by simply getting portable audiodictation devices (you'll want one you can at least plug into your machine).
What this allows you to do is record your audio in a quiet place without needing to haul a laptop around (it's also great for journalistic reporting as you can record discussions or lectures or conferences).
It won't be as great as a high quality mic, but it will be better than most desktop mics in the same price range, and it will automatically convert your recording to MP3 so you don't have to hassle about recording and then exporting.
If battery costs of the recording device seem prohibitive, get rechargeable batteries.
If you're developing speaker orientated videos (EG you're making a point), you nearly always will want to write a script. By writing a script you eliminate the 'uuhs' and 'errs' and 'uhms' and avoid repeating yourself.
Reading from a script can sound monotone and flat, so write in emphasis and be sure to add your own flair to the audio style.
The other advantage of writing a script is you can change segments without redoing the entire video (clean breaks) and you can supply subtitles/a written article for those who hate video.
Keep video intros *very short*. Maximum is 8 seconds, but if you can go without an intro, do so. It's usually best to do a pre-filler (topic introduction), then the intro if you must have one, otherwise try to keep it out.