For my gaming table at home, I got a sheet of 3mm (1/8") plywood, cut it in half (for easy storage) and made a GOOD frame for each half with 12mm (1/2") plywood.
With the same 12mm plywood I made 6 frames (to raise the boards to a table height), and joined two sets of 3 with hinges, to make "Z" shapes. Due to the hinges, these can be folded flat, and in fact, they can be placed inside of the boards frames, so everything can be stored flat against a wall when not in use.
For gaming, I just take the supports, open them to Z form and put the framed board on top.
If playing skirmish games, 1 board usually is enough, but for massed battles, 2 boards side by side make an "official" 122x244cm (4x6') table.
I painted all green, although I usually cover the boards with a green cloth, but also can use whatever color is required for the game we're playing (sand, blue, black, etc.).
Some people can say that 3mm is TOO THIN, And recomend you 6mm, or more.
Actually, I have used those boards for more than 2 years, mounting and taking appart once a week for my gaming group get together, and they are just fine, so I don't believe a greater thickness is neccessary, and only rises cost and weight.
Hope that helps.