How do I reset my progress?

Try using the Prestige. Prestige is really awesome feature which will reset your progress in one particular building (in which you do the Prestige) but it will boost your mining production and you'll get one mining rig to start with. Also, your earnings will increase after doing the Prestige.

You can find more information in the Gameplay section.

On the other hand, you can log out of your account and choose not to load your cloud save, when prompted.

Also worth noting, if you're not logged in onto any account, you'll need to reinstall the game in order to reset your progress.