will be using water based polyurethane for sealing my enclosure, but I have seen people using Polycrylic as well. Just make sure you let it fully dry and all the fumes are gone. I have heard a couple weeks in the sun would do it completely. You don't want to put your dragon in danger.
I am going to be using some plywood for my enclosure floors, but for the sides and back I am using solid wood. I picked up some sealant for it and I plan on using tiles in mine as I have tiles in their tanks now.
From what I have seen they darken up to help absorb the UV and heat and lighten up when not. Our beardies also lighten up when they are happier but that may be just ours.
I am planning to use birch plywood for the enclosure I am building and sealing it with water based sealant. The framework will probably be pine as that is what most of the 2x2 boards are made of, but I am planning on sealing them really good.
I am putting in vents in mine, but I might install...
We just got some larger tile pieces from lowes for our beardies and they love them. I believe they are slate as they have texture and are a big heavier than regular tile.