Go into the cave and wait until the "T" turns to zero and then you can get gold. go to your to the right of the screen to go to your booth, where you can sell your gems. press the shop to receive the options to upgrade your pick or cart. click the crate to collect the gold your cart has collected for you.
the "T" stands for time by the way. NO SPEEDING UP YOU CHEATERS! just be patient.
