The quickest way to teach yourself all these principles I've been talking about is to copy drawings that use them. A lot of 1940s comic books were drawn by professional animation artists who knew their principles well. They would especially knock themselves out on the covers.
These all have
lines of action
construction - perspective
and on top of all that - interesting and tricky camera angles
If you copy these drawings, do it step by step from the basic elements first and then on down level by level to the final details. (Like how I broke down Tom) Don't start with the wrinkles, stripes, spots, textures etc. Do those last - and keep them small and not sticking out too much from the silhouettes.
Ignore the clothes when you first break down these drawings. Draw Goofy's head right through his neck and into his torso in a continuous smooth line of action. Then on top of that, wrap the clothes around his construction. Same with Mickey.
These animal balloons look complex at first, but they aren't if you ignore the details and draw the solid forms first. Then wrap the details, layer by layer onto the forms.
This won't be easy at first, but the more you do it, the sooner it will all make sense and you will start to gain skill and confidence.
Then you can crap on the folks who refuse to learn anything traditionally and still can't draw anything remotely professional or appealing. They will be so jealous of you. And you'll get the better job.