I get error: "attempt to index field 'leaderstats' (a nil value)" How do i fix it?

Easy fix. when you index like thing.name, it's the same as thing["name"], you don't want a string however, you want a variable. Instead of game.Players.name, do game.Players[name]

It seems to me that you don't currently have a leaderboard. Try using this.

First, let's create a Script in the Workspace and name it 'Stats'. Once we've done that, we can begin.

We'll begin with defining our leaderboard values. We'll use a nested array..

local boardStats = {
    { "IntValue", "Money" }
}

Now that we have some values to play with, we'll need our function to usher our leaderboard into existence.

function LeaderBoard(player)
    local leaderstats = Instance.new("IntValue", player)
    leaderstats.Name = "leaderstats"
end

This will make the leaderboard visible in the PlayerList. Now we need to add our leaderboard values. To do this, we will use a for loop.

function LeaderBoard(player)
    local leaderstats = Instance.new("IntValue", player)
    leaderstats.Name = "leaderstats"

    for n in pairs(boardStats) do
        local stat = Instance.new(boardStats[n][1], leaderstats)
        stat.Name = boardStats[n][2]
    end
end

With this for loop, we're traversing the boardStats array, one nested array at a time. We come through the first time, and we'll find that boardStats[1] is equal to { "IntValue", "Money" } and we need to separate these. So we create an instance of boardStats[n][1] and place it into leaderstats. Once we've done that, we name the instance boardStats[n][2].

Last but not least, we need to connect the PlayerAdded function to get this to add values to every new player.

game:GetService("Players").PlayerAdded:connect(LeaderBoard)

Once that's done, altogether we have our leaderboard!

local boardStats = {
    { "IntValue", "Money" }
}

function LeaderBoard(player)
    local leaderstats = Instance.new("IntValue", player)
    leaderstats.Name = "leaderstats"

    for n in pairs(boardStats) do
        local stat = Instance.new(boardStats[n][1], leaderstats)
        stat.Name = boardStats[n][2]
    end
end

game:GetService("Players").PlayerAdded:connect(LeaderBoard)

Your button should then be able to function.