How do I keep a tool when I die after I already bought it?

In filtering enabled, this will never work, no matter how hard you try to develop the client/local side of it.

Make a script, and RemoteEvent, and just below this line

script.Parent.MouseButton``1``Click:Connect(``function``()

Index to your event, as an example.

game.ReplicatedStorage.Event:FireServer(100)

Then, head over to your server script, and put this down

local tool = game.ReplicatedStorage:FindFirstChild("Sword")  game.ReplicatedStorage.Event.OnServerEvent:Connect(function(player,cost)
    local  stats = player:FindFirstChild("leaderstats")
    if stats.Cash.Value >= cost then
     Stats.Cash.Value = Stats.Cash.Value - cost
     local clone = tool:Clone()
     clone.Parent = player.Backpack
     local clone2 = tool:Clone()
     clone.Parent = player.StarterGear
    	end
    end)

A tip is to always put everything that your player needs to see but no one elses in the client, otherwise, put it in the server, if the server doesn't recognize it, when the player dies it will NOT carry your tool over because the server doesn't know you should have it when you respawn.

This setup I gave you is not my ideal set up, but I won't go into explaining that set up as it can get quite advanced when it comes to Filtering Enabled, so I just wanted to go over the concept.