I would suggest going through one or both of these tutorials:
https://t.eeems.ca/ASMin28Days/welcome.html
https://t.eeems.ca/Z80ASM/index.htm

Those are good places to start if you want to learn asm. I’m going to try to persuade you to use Axe Parser for whatever it is you are trying to do.

I assume you don’t know much about assembler for a couple reasons. You listed drawing a shape as a simple task - it isn’t. Also, variables don’t work the way you think they do, there are only registers and memory.
If you aren’t very comfortable with the concept of pointers then I suggest you learn or stick with ti-basic since everything after it relies heavily on them.
Axe can do just about everything asm can and it is much easier to learn and code. I know Axe and assembler quite well and I still code mainly in Axe because it is easier to use and gets the job done. Something that I can create in minutes in Axe can take a half hour in asm

Let me say it again: Unless you are trying to do some REALLY crazy things or have other assembly programming experience I would go to Axe for whatever you are trying to create.

ASM isn't very hard to learn, but if you want to do anything interesting with it, you need a good understanding of how the CPU works. Axe simplifies things a great deal by providing a ton of convenience functions for the most common tasks. Makes things much easier than building from scratch in ASM.
Also, assembly isn't necessarily faster than Axe, but if you are really good at it, then you'll be able to write smaller and more optimized programs, and it's quite fun.