There are a few threads on here about what supplies you need to get started, I'd search through those.
When I started I bought TONS of tools! I'm not joking, I starting researching there are just so many different techniques to cake decorating. I bought the huge 3-level Wilton tool cady, a cricut, isomalt, anything Wilton I could get my hands on...I have a room full of tools and I haven't even used half of them.
I've replaced most of my Wilton pans with higher quality. Cake decorating is an expensive hobby/profession.
Depending on your skill set and future goals I would start with some good quality pans (Magic Line) avoid the ones with slanted edges. A good quality serrated knife for leveling and torting your cakes. Many people make their own fondant but if you haven't made it before its a good idea to buy some first, that way you get a feel for the texture. A Lazy Susan is great for a turntable, some offset spatulas and a bench scraper (for smoothing icing-very important for fondant). Some kind of rolling pin and a smoother. These are what you'll need to get the cake covered.
Most of your sculpting tools you can get in the clay isle rather then among the cake decorating supplies, they are much cheaper. Many tools can be substituted for things you already have around the house. You can slowly add to your collection, petal dusts, food color, exacto knife (probably use this more then anything or a scalpel), cutters if you want to focus on flowers. It just depends on what you want to make.