I use (3) 2'x4' folding leg tables I got from one of the big box hardware stores. This give me a 4'x6' area for WW1 aerial wargaming. I was using 4'x6' for WW2 ground warfare as well but lately I cut it down to using (2) 2'x4' tables, giving me a 4'x4' area.
The reason I cut it down was I play mainly skirmish games and realized the first several moves were mainly moving one side or the other into position before any combat took place. Since then I place a 3'x3' mat on top of the table to cut down on maneuvering and get right into the shooting. This also give me some room on the table to put my dice, cards, rules, etc. Here's an example of a game using One-Hour Skirmish Wargames Rules in a 3'x3' arear: