If you are sure that you want to stick with cake decorating for longer, consider buying a whole set of modelling tools. It’s much cheaper to buy a whole set than to buy each tool separately. You won’t probably use all of them on daily basis, but they will come in handy from time to time.
Go through on-line reviews before deciding on the brand.
You will also need a non-stick rolling board. I suggest buying a large one instead of a small one (you’ll need the large one to roll out the sugarpaste for cakes anyway). The size of the one I have is 60 x 50 cm. I grease the board with a small amount of white vegetable fat (Trex) before rolling out the paste.