If you want it so that you can see what other players are doing, use AI Scripts (Turn Shared Vision On). Make sure that, say, you are P1 and you want vision from P2, that you turn on Shared Vision (AI Script) for both players.
[Players]
Player 1
[Conditions]
Always
[Actions]
Turn on Shared Vision for Player 2
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[Players]
Player 1
[Conditions]
Always
[Actions]
Turn on Shared Vision for Player 1
(It only works if both players have shared vision activated).
If you want to see the WHOLE map, even areas that are vacant, playe multiple Map Revealers, for either you or someone who you want to see the whole map as well (Shared Vision AI Script), all around the map. I usually place a revealer, count 12 spots over by using the arrow keys, then placing another one.