You can hack things in this game but you have to remember to revert the gold coin value after you're done otherwise the cheat detection will get you.
If you change the gold coin value to whatever amount you like by searching encrypted dword. There is a tab where you can convert gold to silver so the easiest way is to convert 1 gold at a time until you find the value you need to change. Incidentally the value in my game was always the one that was somewhere between 400,000 & 499,999. Not sure if that would be the same for everyone though. Once you've changed the value then you can convert whatever amount you like to silver coins. I did 5-10 million and that was more than enough. Probably a few million is ample.
You can use the gold coins to upgrade any weapons / vehicles and to buy any special offers as well that might be available in the shop. You can get some weapons, armour, ammo etc.
You can also hack skill and perk points too by using encrypted dword. I reverted them back once I was done but dont know if it's necessary.
Just remember once you're done revert the gold coin value back to what it was and then you shouldn't be detected by the cheat detection.