To change the resources the player stats with navigate to the BP_PlayerFarmingComponent then open the Class Defaults and search for Resource and you’ll see the settings shown below.
Here you can set the starting amount of each resource such as Tomato, Corn Seed, Wood etc. You can also create new resources by clicking the + button next to the Resources drop down, once you add a new resource you can set a resource name and resource amount. You can remove resources by clicking the down arrow next to its index drop down and selecting Delete.
You can also set the cost of different plant interactions using the Cure Resource Cost, Fertilize Resource Cost and Water Resource Cost. These are the resource cost of these actions.