I know it expands and stuff, so what are my options really?
I don't really want 2x6 from HD since it's S4S. I want rough cut since I'll plane and join them. what grade of 2x would you recommend?
When you say 2 X 6 that immediately calls for dimensioned lumber, softwood, construction grade. It is not available "rough sawn"., but as you say S4S. So then we think hardwood, rough sawn or maybe some softwood species from a mill? Right? What species?
You got a source for this?
Now as far as wood movement there's a whole bunch of info on what to do regarding attaching a top to the skirt and breadboard ends IF you are going that way?
Next issue is joinery. What method ..... mortise and tenon, nut and bolt, pocket screws?
Next issue is design. Cross brace "X" type, vertical legs? You gotta have a plan before we can be much help and you gotta really understand wood movement, EMC, moisture content, "kiln dried" and acclimation to the environment to have a successful project.
Finally, you gotta have a bunch of clamps ready to go and a nice work surface IF you are gluing these planks together:
Door Build from 2 Xs and 1/4" ply