Collect money:

Use the two free Dig and Raise tools (toggle in corner) to dig and put back sand. Sometimes you will find treasure in sand, which you can click on to sell for money

Expand your arsenal:

Open the store to buy more tools with money to help you dig sand faster. If you want to, you can sell the boss for money and afterwards you will never see him again if you're a MONSTER.

Alternatively, you can simply etch designs into the sand instead of digging for treasure.