https://www.knorr.com/us/en/p/spanish-rice-side.html/00041000022685

Depending on your level of struggle, these rice packets cost about ~$1.25 USD and cook in 7 minutes, you just gotta stir 'em a bit.

To that I'll add some protein, either some sausages I cooked on the George Foreman grill and sliced up or a packet of flavored tuna. This is mostly no effort or unattended.

For veggies, I'll steam up something fresh or microwave some frozen mixed veggies. Either way this can be done in 3-5 minutes, unattended.

Some effort, but still very low. You can get everything started at once while you stand there and stir the rice packet on the stove, everything should wrap up in less than 10 minutes and you'll have a relatively complete and filling mill for hopefully less than $5 USD but I don't even fucking know anymore with inflation, tariffs, and out of control groceries. Should still be more cost effective than a lot of alternatives, though.

EDIT: The rice packet can honestly be quite a bit for a single person, depending. You may want to pad it out with a few more things like mushrooms and beans, then you can split the meal in two. Eat half now and save half to be microwaved later to stretch it out and for when you have no prep time at all.