That's a tough question to answer because the type of project you are cutting determines what type of wood you need. Every wood has its own distinct properties. Plywood (especially baltic birch) is good for portraits and many other projects, pine is good for thicker projects especially if they will be painted, hardwoods are great for many things but you may need to be able to either buy them in thinner thicknesses or plane them to the desired thickness. Some woods are very tough, and some are relatively easy to break. A few of the hardwoods like cherry and maple are great, but have a tendency to burn when the cutting is too intricate. Tell us what you want to build and what wood you have available and we can help a lot more.
