definitely start with 2D stuff first; even in 3D designs you will use a lot of 2D techniques and just add more things to your arsenal.
Really, start with an idea, then build that end to end. I started with a simple square box (from the video series above), then I used a logo as the shape for the box and then I made a box with a design carved on top. Being able to do that gave me the confidence to a next level… (lots of multilayer name signs with cityscapes in the back ground etc etc)… until I got to the thing I wanted to build originally, which was a 3D terrain carve of the area I lived in at the time (pictures at Red Pin Terrain carve)
What seems overwhelming at first will get a lot simpler once you have done a few designs. At least for me I had to learn the wood/machine side of things from scratch while I’m naturally more comfortable with the digital side of things. But doing an end-to-end design (like a box, see video) really helped me connect both worlds together to have it “click”.