How would I use something Similar to waitForChild on a table?

So in your case you'll be waiting for a table to hold a value or player to be added to the table? I would check a table for the existence of a key value, instead of value, in order to make it easier to wait for the existence of playername added to it.

I suppose one thing you could do is run a function that converts your current table structure temporarily so that the values become keys and then do a check for that key... you could then run a loop that returns true when the key is found.

function waitForTableValue(tbl,value,timeout_seconds)
        -- do some checks
        if timeout_seconds==nil or timeout_seconds==0 then
            timeout_seconds = 3 -- default to timeout_seconds
        end
        if value==nil then
            return false
        end
        local start_time = game.Workspace.DistributedGameTime
        -- you could also do a type check on tbl, but below should suffice... just be sure to make tbl a table!
        if tbl==nil or #tbl==0 then
            return false
        end

        local tmptable = {}
        for i,v in pairs(tbl) do
                tmptable[v] = i
        end
        while tmptable[value]==nil and game.Workspace.DistributedGameTime - start_time<timeout_seconds do
            wait(.1)
        end
        if tmptable[value]~=nil then
            return true

        end
        return false
    end

The ":WaitForChild()" also same as like":FindFirstChild()".

The call ":FindFirstChild()" does as it says. It finds the first child of a parent of which you name it. There must always be an argument, most likely a string. Let's see how it works:

game.Workspace.Figure:FindFirstChild("Humanoid")

If you think I explain too hard, explain not cleary, want to see more information with ":FindFirstChild" , click here.

Also, ":WaitForChild()" is find the thing that doesn't exist at testing mode,when you start the game, the thing will appear at the game. Like this :

local part = Instance.New("Part")
part.Parent = game.Workspace
part.Position = Vector3.new("0,0,0")
game.Workspace:WaitForChild("Part").BrickColor = BrickColor.Random()

If you think I explain too hard, explain not cleary, want to see more information with ":WaitForChild()" , click here.

Hope I helped.Thanks for reading!