game.Players.PlayerAdded:Connect(function(player)
        script.Parent.Touched:Connect(function(hit)
            if hit.Parent:FindFirstChild("Humanoid") then
                local leadstats = player:WaitForChild("leaderstats")
                local coinss = leadstats:WaitForChild("Coins")
                local coins = coinss
                coins.Value = coins.Value + game.Lighting.cakes.Value
            end
        end)
    end)

u cant do value in a variable this should work

When you assign a variable to a value in Lua, you assign that variable directly to that value. You do not point to that value, or save a path to that value. Consider the following code, for example:

t = {}
t.foo = "bar"
x = t.foo -- Assign x to t.foo.
print(x) --> bar
t.foo = "baz" -- Update t.foo.
print(x) --> bar (x is not updated.)
x = t.foo -- Update x to t.foo's new value.
print(x) --> baz (x is updated.)

Likewise, assigning x to a different value would not change the value of t.foo:

x = "hello"
print(t.foo) --> baz

Your issue is that you are directly updating the coins variable, which is in no way related or linked with coinss, on line 08. To the program, it is simply some arbitrary piece of data. Instead, you should update coinss.Value directly.

Just a few small nitpicks, you should be using ServiceProvider:GetService to get all services except, optionally, Workspace.

Here's the updated code:

local cakes = game:GetService("Lighting").cakes

game:GetService("Players").PlayerAdded:Connect(function(player)
    script.Parent.Touched:Connect(function(hit)
        if hit.Parent:FindFirstChild("Humanoid") then
            local leadstats = player:WaitForChild("leaderstats")
            local coinss = leadstats:WaitForChild("Coins")
            coinss.Value = coinss.Value + cakes.Value
        end
    end)
end)

I hope that this helped!

Problem

Do not put .Value in variables to change value's, names and more.

Example:

-- Incorrect
local value = workspace.IntValue.Value --< Default value: 1
value = value + 1
-- Value of object = 1, why? wen you change a value from variable this only change in script, not in value.

-- Correct
local value = workspace.IntValue --< Default value: 1
value.Value = value.Value + 1
-- Value of object = 2, this worked but you changed it in object, not in variable.

Correction

You dont need to detect player added, you can get character with Touch event using Players:GetPlayerFromCharacter(char)

What Players:GetPlayerFromCharacter(char) make?

• GetPlayerFromCharacter returns the Player associated with the given Instance, or nil if one cannot be found.

Example:

script.Parent.Touched:Connect(function(hit)
    if hit.Parent:FindFirstChild("Humanoid") then -- Check for humanoid
        local plr = game.Players:GetPlayerFromCharacter(hit.Parent) -- Get player
        if plr then -- Check player
            print("Got player!")    
        end
    end
end)

Also for fix your problem do not use .Value in variables for change a value. You can simple remove the .Value from variable and put coins.Value = coins.Value + ...

Fixed script:

script.Parent.Touched:Connect(function(hit)
    if hit.Parent:FindFirstChild("Humanoid") then
        local player = game.Players:GetPlayerFromCharacter(hit.Parent) -- Get player
        if player then -- Check for player
            local leadstats = player:WaitForChild("leaderstats")
            local coins = leadstats:WaitForChild("Coins")
            coins.Value = coins.Value + game.Lighting.cakes.Value
            --< Not is good way to storage items in Lighting.
        end
    end
end)

Hope it helped :)

Wiki pages

GetPlayerFromCharacter

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