As long as your damage is higher than the enemy's health, you will win. All other stats are irrelevant.
The second weapon, which is made using the ingot from the fifth area is the best thing to spend money on.
The most annoying thing about this game is clicking to increase the level of the enemy. After leaving the game running for 30 minutes, I can now increase my enemy level from 19000 to 35000, but you can't hold down the button or choose the level. It has to be done in single clicks. Even using an autoclicker, this will take half an hour.
Also, once the enemy level is above 9999, the final digit is hidden, so although I am fighting at level 19107, it says 1910.
Despite all that, I am still playing. It's a very simple game which should have been improved upon, but has obviously been left to gather dust.