I broke my pinky metacarpal bone. What is the easiest and cheapest thing I can do to fix this?

See your doctor. Tell your doctor your situation and then follow his instructios to the letter. Many patients will remove their splint/cast for reasons that don't always make any sense but this can compromise the result of treatment. Not to treat make cost you more to fix latter.
Cheap fracture. Cheapest may be to do nothing now but remember if you have a bad result and in the end you miss work and later have issues because you tried to skimp.
Depends on break. Needs evaluation, xray to see if displaced fracture or not (don't want nerve, blood vessel damage, not too mention deformity or poor function/pain after healing). Cast or splint. Healing generally in about 6 weeks. Displaced fractures sometimes need surgery to repair.