Write a relatively simple C program that does something useful that you understand thoroughly, then generate intermediate assembly code from your C compiler, with optimization turned off.
That way you get a problem that you already know how to solve in a .s listing that you can inspect and modify to your hearts content.
Then try to optimize it, make it run quicker by rearranging stuff.
You'll learn lots that way and the barrier to entry is low.
Write a relatively simple C program that does something useful that you understand thoroughly, then generate intermediate assembly code from your C compiler, with optimization turned off.
That way you get a problem that you already know how to solve in a .s listing that you can inspect and modify to your hearts content.
Then try to optimize it, make it run quicker by rearranging stuff.
You'll learn lots that way and the barrier to entry is low.