Precision is key. Digging deep into the paystreak (the blue/gold layer on your map) is more efficient than clearing topsoil.
This is where the big money is made, but the overhead costs (rent, fuel, and parts) skyrocket. Gold Rush: The Game Free Download (v1.5.8.15125...
Only take a loan if it immediately buys equipment that increases your hourly yield. Interest can eat your profits quickly if you aren't digging 24/7. Precision is key