Go with OAK laminated MDF.
3/4" thick sheets (4' x 8') are often on sale for around $33 at the midwest home improvement store called Menards. If you only have Home Depot/Lowes, I dont think they stock it normally, but you can have them special order it... expect to pay around $40+ at those places
It works just like MDF, but has 2 sides that have been laminated with real oak laminate. I just built 2 eight foot long bookcases out of this, and it stains and poly's just like real oak (because the last 1/32" *IS* pure oak.)
I dont think they make 1 sided versions of this (since you don't need oak on the inside) but it's a LOT less expensive than solid wood!
And on the edges that you don't want to use T-Molding on, you can simply iron on 3/4" oak laminate yourself and trim with a utility knife. 8' of that is only 99 cents most of the time.
The oak is usually red oak, and stains the 100+ shades of stain you can buy.
Alternately, if you don't like the richer/darker color and grain of red oak, you can also get at Menards, Birch laminated MDF for about the same price (+/- $1 a sheet). It is lighter and whiter, but stains well, a LOT better than solid pine would.
And by the way, the laminate is NOT plastic/vinyl and NOT formica. We're talking about a lathe cut spiral of oak from a tree and then hot glued directly to the side of the MDF at the factory. Once stained and polyed, you CANNOT tell it from a solid piece of wood, other than by weight (MDF is heavy)
Good luck!