If you do start with a smaller table, knowing that you will eventually extend the Y axis, I would suggest looking at these blocks:
As far as material and height for the table, I think it boils down to personal preference, material cost, and availability. I have a ping pong table with a sheet of MDF screwed to the top for the spoilboard. I might eventually build a nice torsion table, but the ping pong table was free and is actually working well for me.