For 3D work you will want an 1/8" ballnose. Dremel has an 1/8" ball nose bit (9905) that is solid carbide. That might be a starting point. There are other suppliers of bits with 1/8" shanks that you could look into such as Bits & Bits (<-link)
I'm not sure if your aware of it but that image you posted is of a door about 6 feet tall!
I have never experienced a V90, and it might be great, but I would strongly suggest getting a machine which can fit at least a router spindle with speed control instead of a dremel.
A dremel tool is very light duty for 3D wood cutting, and a router spindle with even 1/4" collet will give you more flexibility and variety when looking for tooling to suit your specific jobs. Having said that, I don't know what type of work your looking at doing, and if its small wood carvings up to about 6 or 8 inches, then maybe a dremel would be fine.....just m2c.
Ok, I had a quick look at the V90. The site doesn't say how much it is, but it does say that other tool holders are available instead of the Dremel tool holder. I would suggest investigating that. Check if the performance of the machine changes with a heavier router in place of the dremel too.
Regarding your other questions about bits -- I prefer solid carbide: start with an 1/8" ball nose, an 1/8" straight cutter. Start with 6 of each. Expect to break several bits as you learn the proper RPM and speed to move the tool.
The ball nose is for 3D work and the straight cutter is for cutting out the finished piece. Learn how to use these two basic bits in these sizes before you try larger or smaller bits. Depending on the depth of the carvings you may need to get longer bits, but otherwise use the shortest bit possible to reduce runout.
Smaller bits give finer detail but are easier to break.
The material you cut can also influence your bit choices: plastic, solid hardwood, softwood, plywood, MDF, MDO, foam, marble, etc.
If you want to do some Vcarving then get some engraving bits as well in different angles.
-----
Since it was mentioned earlier, I too would recommend that you look at a spindle rather than a dremel. You may be frustrated if you need it for consistent production 3D work, but if you are looking at this as a machine for learning CNC and don't mind doing some cleanup by hand then the dremel will be fine.
Explanation:
The dremel has more runout, i.e. the bit wobbles rather than staying dead center - particularly with axial (side-to-side) loads. This means that your edges and corners may not be crisp and clean. If you plan on doing cleanup by hand then this isn't an issue.
Many artists do their rough cutting with a machine but finish it by hand. (I still occasionally do handwork on some pieces just to help bring them to life.) However, if you are expecting fine detail straight off the machine for 3D work you may be disappointed with the dremel.
)
