In order to make your farm larger and more sucessfull, you're going to need to have some upgrades. The person who will upgrade your buildings is Gotz, who lives just south of your farm. If you need to have your farming tools upgrade then you would talk with Saibara. You can reach the blacksmith shop by leaving your farm via the exit to your house, then entering the first building you come across on your right.
Each type of upgrade requires materials that you will have to gather. Gotz's upgrade requres you to chop a lot of wood with your Ax. For Saibara, you're going to need to dig up ore from the mine next to the Hot Springs on Mother's Hill. Both men will tell you how much each upgrade will cost and how many days it will take them to complete your upgrade. Most upgrades can only be completed once, but Gotz has a few that you can do over and over again.Farm Building Upgrades