How i win 99% of the times i play:
Step one: sell your left arm. If you're not sure which one i mean, i mean the protagonist's left.
Step two: Buy nothing until bamboo, it's a long ranged weapon that helps a lot.
Step three (optional): When you have the chance, you can buy the spear. It's basically the bamboo, but better.
Step four: buy the mace, and complete the final fight.