Or you can skip all the leveling your merchant, the grinding, etc, by buying and spending gems. The gold cost is hefty enough that any serious helping the guild or upgrading the heroes or any other serious upgrades is not possible, unless you want to seriously delay the shop size upgrade.
It takes half a week to upgrade, during which no other upgrades are allowed.
You can spend half a year leveling up, grinding gold like a madman, and then buy one of the shop size upgrades. As someone that has played copious amounts of Shop Titans on mobile, I can tell you that there is significant P2W mechanics in ST as well.
