How do I make this script take away a value from the player?

For your shop, you will need to use Leaderboards. There's other ways to do that too, but it's better to do with that, as Roblox handles updating the player list.

Supposing you made yourself some Leaderboards and you put the money counter in as "Money", here's your finished script:

script.Parent.DialogChoiceSelected:connect(function(player, choice)
if choice == script.Parent.C then
if player:WaitForChild("leaderstats").Money.Value >= insertrequiredmoneyhereA then -- WaitForChild just in case
player:WaitForChild("leaderstats").Money.Value == player:WaitForChild("leaderstats").Money.Value - insertrequiredmoneyhereA -- As paying for something needs money, we take off the required money from the player's wallet.
--In addition, you can freely refer to the value which is going to be edited itself, as i did above. The value it finds at that moment gets used.
gunB = game.Lighting["Burger"]:clone()
gunB.Parent = player.Backpack
else
--Insert script on not enough money here. Unless you put script that gives the player the item in this space, no item will be given to the player if he doesn't reach insertrequiredmoneyhereA.
end
elseif choice == script.Parent.D then
if player:WaitForChild("leaderstats").Money.Value >= insertrequiredmoneyhereB then
player:WaitForChild("leaderstats").Money.Value == player:WaitForChild("leaderstats").Money.Value - insertrequiredmoneyhereB
gunC = game.Lighting["Pizza"]:clone()
gunC.Parent = player.Backpack
else
--Again, insert script on not enough money here
end
elseif choice == script.Parent.E then
if player:WaitForChild("leaderstats").Money.Value >= insertrequiredmoneyhereC then
player:WaitForChild("leaderstats").Money.Value == player:WaitForChild("leaderstats").Money.Value - insertrequiredmoneyhereC
gunC = game.Lighting["Ice"]:clone()
gunC.Parent = player.Backpack
else
--Insert script on not enough money here, once more
end
elseif choice == script.Parent.F then
if player:WaitForChild("leaderstats").Money.Value >= insertrequiredmoneyhereC then
player:WaitForChild("leaderstats").Money.Value == player:WaitForChild("leaderstats").Money.Value - insertrequiredmoneyhereC
gunC = game.Lighting["Cola"]:clone()
gunC.Parent = player.Backpack
else
--Finally, insert script on not enough money here.
end
end
end)




--By the way, did i tell you to insert script on not enough money here?!?!?!?!?!??!?!?!1one!??!?!?!eleven!?!?1one1111!

What You Need To Do

You need to index the Currency Statistic of the player's leaderstats. Once you do this then you can check if the value is greater than or equal to your specified price with the >= operator.

Leaderboard Setup

The standard leaderboard setup goes like this;

• Player

• • leaderstats
• • • stat

The 'leaderstats' value must be named 'leaderstats' and whatever values you put in there will be part of the leaderboard.

Efficiency Fixes

Name all the dialogchoices to correspond with the food they'll give!!

Make a table full of the items and their prices, you can then iterate through this table with a generic for loop. You can then index the currency leaderstat, check if the player has enough, subtract the price from their leaderstat, then give them the object.

Code

--lets make a table, this table will be full of the names of the food and their prices.
local items = {
    ['Burger'] = 25, --A burger will be 25 currency.
    ['Pizza'] = 50,
    ['Ice'] = 75,
    ['Cola'] = 100
}

script.Parent.DialogChoiceSelected:connect(function(player, choice)
    --Iterate through table
    for i,v in pairs(items) do
        --Check if it's the right choice
        if choice.Name == i then
            --Define the leaderstat. MAKE SURE 'CurrencyStat' IS THE CORRECT NAME.
            local stat = player.leaderstats.CurrencyStat
            --Check if they have enough
            if stat.Value >= v then
                --Give them the item.
                game.Lighting[i]:Clone().Parent = player.Backpack
            end
        end
    end
end)