For a plastic kit, there really isn't a better one than the Revell Snowberry. It's a nice size, lots of detail provided, conversion is simple but needs a bit of thought and still a very reasonable price.
To scratch build, look up Glynn Guests builds. As originated, they tend to be a bit basic, but can be detailed up - you incrementally create your own challenges. If balsa is used, it does need plenty of care and attention, essentially it is pre-rotted wood and really likes damp. By that, I mean that untreated it absorbs water very readily. Ply generally results in a stronger model, but still needs treatment to keep wet out of the structure. If you look around on the forum, you will run into the SD14. That is huge, and made of card, so there is a very wide range of materials that can be used, but some combine ease of build, strength and possible finish better than others.
