Gold and gold upgrades

Gold can be used on very powerful upgrades that can speed up your progress significantly or jump ahead in time. It can also be used to buy extra shops or to hire workers without losing anything (except for the 300 gold cost obviously)

Forever multiplier

This boost multiplies the profits of all of your businesses. Each time you buy a forever multiplier, it ADDS that amount to the previous multiplier.

Ad view boost

This boost increases the multiplier that you get when you watch an ad. Each purchase ADDS 3x to the previous multiplier.

Forever speed boost

This boost reduces the amount of time that it takes to get profits from all of your businesses. Each purchase MULTIPLIES the previous multiplier by 1.07. The cost increases by 5 gold per purchase.

Time skips

Purchasing a time travel will give you that amount of time of profit instantly. I wouldn't recommend purchasing these, as the cost is really high and gold can be used on much better benefits.

I also wouldn't recommend buying shops or hiring workers with gold either, as they are also one time/temporary benefits. Save your gold to purchase long-term benefits!