If you have multiple cards of the same type, fuse them for money and they will get better. Keep opening chests and get as many cards as possible.
Digging
Digging down is not always the best direction. Do not always tap the square below, especially if you have the space and have a tile that will break in one tap near. Avoid the hard to break tiles because they will drain your pick’s power. If you see special stone squares around you, try getting them. Even though you will not get deeper, you will earn money to upgrade the pick. After it can take over 60 digs, begin concentrating on depth. While digging, you may find grenade boxes, gas, and other boosts that will help break tiles. Always collect them because they offer free digs. The least useful boost is the dynamite, which breaks all the tiles horizontally. However, all the others, especially grenades, are very useful.
Gems
Spend gems to purchase new cards of Rare and better quality. You can earn up to 70 gems by inviting ten friends to the game.
Money
Tap the "Free Stuff" button to watch an advertisement and get the chance to get money, and rarely a special box that can hold very good cards. Do not spend the five dollars to reshuffle if you do not like the three cards that you are given at the start of a game. Save your money so you can upgrade your pick faster.
Pick
Upgrade the pick at every opportunity. A better pick will let you dig longer and gives you the chance to earn more money, getting cards, and fuse the cards you already have.