How can I find a player from a surface GUI button?

I have been trying to make a surface GUI that shows how long someone has been working and how much they have earned (As well as giving them money.) However I can't figure out how to find the player who clicked the button. Right now I have it firing an event but that would still give everyone on the server money. Any tips?

Server Script:

------------------Declerations------------------
TPH = script.Parent.Frame.PH1  -- Time place holder
MPH = script.Parent.Frame.PH2  -- Money place holder
Btn = script.Parent.Frame.Button
O = false --True or false for onClicked 
Timer = script:WaitForChild("Timer")  --Base number for stopwatch
BT = script.Base_Money
MPS = script.Money_Per_Second

------------------------------------------------
---Creation and nameing of User pinging event---

local ReplicatedStorage = game:GetService("ReplicatedStorage")
local ClientPing = Instance.new("RemoteEvent", ReplicatedStorage)
ClientPing.Name = "ClientPing"

------------------------------------------------
------------------Main Script-------------------





function onClicked()
    print("clicked")
    if O == true then
    ClientPing:FireAllClients(O)
    print("Ping sent")
    Btn.BackgroundColor3 = Color3.fromRGB(97,255,107)
    Btn.Text = "Start"
    O = false
    wait(3)
    BT.Value = 0
    Timer.Value = 0
    Timeset()
    Moneyset()
    else
    ClientPing:FireAllClients(O)
    print("Ping sent")
    Btn.BackgroundColor3 = Color3.fromRGB(255,0,0)
    Btn.Text = "End"
    O = true
    end
    print(O)
    while O do
        wait(1)
        print(O)
        BT.Value = BT.Value + MPS.Value
        Timer.Value = Timer.Value + 1
        Timeset()
        Moneyset()
    end 
end

------------------------------------------------

function Timeset()
    local formatString = "%i:%.2i"
    local seconds = math.floor(Timer.Value % 60)
    local minutes = math.floor(Timer.Value / 60) 
    local output = formatString:format(minutes, seconds)
    TPH.Text = output 
end

------------------------------------------------

function Moneyset()
    MPH.Text = BT.Value
end





Btn.MouseButton1Down:Connect(onClicked)

Local Script: The local script is not done but it would give the player money while O == true.

Plr = game.Players.LocalPlayer
wait(1)
print("run1")
local ReplicatedStorage = game:GetService("ReplicatedStorage")
local ClientPing = ReplicatedStorage:WaitForChild("ClientPing")





function ClientPing(O)
    print(O "ClientPinged")

end








ClientPing.OnClientEvent:Connect(ClientPing)

P.S. I am new to scripting so I am going for function over beauty but any corrections would be very much welcomed.