How do a make good statistics for an XP system?

So the scripts are already figured out and I need statistics. because if I kill a mob(5 exp) I get from lvl 0-3 and it's kinda broken

game.Players.PlayerAdded:Connect(function(plr)
    local exp = script.EXP:Clone()
    exp.Parent = plr
    local lvl = script.Lvl:Clone()
    lvl.Parent = plr
    local mxp = script.MaxEXP:Clone()
    mxp.Parent = plr
    local stp = script.Strength:Clone()
    stp.Parent = plr
    mxp.Value = lvl.Value * 2.3
    exp.Changed:Connect(function()
        for i = 1,3 do
        if exp.Value >= mxp.Value then
           lvl.Value = lvl.Value + 1
           stp.Value = stp.Value + 1
           exp.Value = exp.Value - mxp.Value
           mxp.Value = lvl.Value * 1.8
        wait(0.01)
        end
        end
    end)
    plr.CharacterAdded:Wait()
    plr.Character:WaitForChild("Humanoid").MaxHealth = lvl.Value * 1.3 + 100
    plr.Character:WaitForChild("Humanoid").Health = lvl.Value * 1.3 + 100
end)

the amount of dmg also increases for the sword, and i feel that it is a bit too much. the standard dmg is 10, and i need to increase it according to stength.