This can be done easily in the tutorial area.
After completing/skipping the tutorial head straight up the stairs, make sure you have a crafting table on you, and keep going until you see a building on your right with an enchanting table in it. Access the chest on the left and take out an iron pickaxe, iron axe and iron shovel.
Equip the iron pickaxe and break 8 blocks of cobblestone on the ground, place down your crafting table(or make one from nearby wooden planks) and make a furnace. Use the axe to break some wooden planks off the wall, then place them in the furnace.
Now take out your shovel, and head down the stairs opposite your building to the docks. Jump straight in the water and there is clay deposits straight ahead on the edges underwater. Once you have gathered 3 pieces of clay, head back to your furnace, put them in and wait for it to make 3 clay bricks.
Now turn those 3 bricks into a pot plant which can be made in your crafting table under the decorations tab.
15GS in 1-2 minutes.