How do you Force a Player to Wear an Outift?

To do it for a Group you could do Player:IsInGroup(ID). Example:

game.Players.PlayerAdded:connect(function(Player) -- Once a player is added
    if Player:IsInGroup(372) then -- Check if their in the group
        -- code here
    end -- End the if statement
end) -- End the PlayerAdded function

To do it for a Team you could check their TeamColor by Player.TeamColor. Example:

game.Players.PlayerAdded:connect(function(Player) -- Once a player is added
    Player.CharacterAdded:connect(function() -- Once a Character is added to the Player
        if Player.TeamColor == game:GetService("Teams")["Scripting Helpers"] then -- Check their team
            -- code here
        end -- End the if statement
    end) -- End the CharacterAdded function
end) -- End the PlayerAdded function

And for both of those, you could create a new Shirt and Pants on the Player's Character, though you might want to delete their old one first.

To delete their old one:

game.Players.PlayerAdded:connect(function(Player) -- Once a player is added
    Player.CharacterAdded:connect(function() -- Once a Character is added to the Player
        if Player.TeamColor == game:GetService("Teams")["Scripting Helpers"] then -- Check their team
            wait(1) -- Give it a chance to load, now thinking about it ChildAdded might've been better
            for _,v in pairs(Player.Character:GetChildren()) do -- Gather everything in their Character
                if v:IsA("Shirt") or v:IsA("Pants") then -- Check if its a shirt or pants
                    v:Destroy() -- If it is, destroy it
                end -- End the if statement
            end -- End the for _,v in pairs statement
        end -- End the if statement
    end) -- End the CharacterAdded function
end) -- End the PlayerAdded function

To create new one(used random shirt and pants cause Scripting Helpers doesn't have any):

local Shirt = Instance.new("Shirt",Player.Character) -- Create new shirt
local Pants = Instance.new("Pants",Player.Character) -- Create new pants
Shirt.ShirtTemplate = "rbxassetid://363587040"
Pants.PantsTemplate = "rbxassetid://363587589"

It's important to note that for the ShirtTemplate and PantsTemplate, you'll have to remove 1 or 2 from the ID(363587042 to 363587040, and (363587591 to 363587589),.

Sorry I can't really explain it any better.