You get 100 Brain points to start. Each hint costs 10 points. You regenerate 50 points a day, capped at 200. That's the economy.
Spend a hint when: you've written your attempt, gotten a tutor response, and still don't know the next move. Do not spend a hint before your first attempt. The tutor will refuse anyway, and it wastes points to try.
Prefer level 1 hints — 'name the concept.' They cost the same as level 5 but train a more transferable skill. If you find yourself always jumping to level 4 or 5, that's a sign you're not sitting in the discomfort long enough. Sit longer.
Reveal is not a shortcut. It's a debrief after struggle. If you're using Reveal on the first attempt, you're using the wrong tool for the job.