Cheap option: learn how to draw. It’s not as hard as it sounds, and I’m sure you’ll make great things! Alternatively you can get into 3D modeling

Cheap and fast: If you are willing to deal with the criticism of using AI, you can use stable diffusion to generate your anime girl. The easiest way is to use Automatic101’s stable diffusion UI, and pick a few interesting models from sites like CivitAI. It’s open source too, but require setting up and not potato hardware

Cheaper and fast: you can use AI horde Stable Diffusion. It’s a service to generate pics run by volunteers, (including me sometimes), no login required (although recommended for higher queue priority). It’s fully open source still, and only need a web browser

There’s other AI services too, but most would make sell your soul to their corporate overlord. I won’t judge you for using those, but as a fellow Linux user, I’d figure you’d prefer the good old foss first