Ok so I have a similar problem for limbs, but for torsos I’ve developed a sure fire way to make something unique and sticks to part limitations.
Here’s my process:
1). Firstly, load up Bricklink and Stud.io
2). Find every color you want to use. Grab pieces in these colors, preferably ones you own or have a different color of.
3). Remember to grab Liftarms and Connectors, as these will be the lifeblood of the torso.
4). Start forming the torso around a central piece, usually the Metru Lower Torso or the neck Socket. This will allow you have an easier time and potentially swap the pieces out later for a different connection.
Sidenote, anything you build should be replicatable IRL, as you find out how well it holds up and if it has any major problems
5). Remember this takes time and TONS of trial and error. I’m currently on the 28th version of my Nidhiki and he’s finally 99% done. In fact, he was made from a limitation of only Green parts I owned, as I counted them out and used them inside Stud.IO.
6). Try building something just for the heck of it, as that’s how I came up with my Dume, as he was originally a Toa Naho I built randomly.
7). Towards the end of the process, try finding armor pieces that will got the shape and overall look of the character. Like my Tuyet was built around Metru meets Nuva, giving her a Smooth meets Pistons and Ridges style. If you want, you can also rebuild the torso to match the armor style better.
8). Sometimes a build will just end up being incompatible with your current idea. For those, save them away in an extra file, that way you can always go back to them and possibly salvage something.
Finally 9). It’s very tempting to compare it to other creations out there but the fact is practice makes better. Your first build is gonna look vastly different from your 30th. Yes it’s never gonna be perfect, as all creations will have a flaw in them but if you put in the time and effort, then that won’t matter. You’ll have something you’re proud of and might even inspire someone else to become better.
I hope this helps you out and I can’t wait to see what you make with all of the advice everyone’s given. Good luck!