DataStore with table not saving?

Here's your code, this also helps it so that if the script loads longer than usual, all players will get their data loaded.

This should also fix your saving issue, and yes, you are using table.insert in a correct manner.

local Players = game:GetService("Players")
local DataStoreService = game:GetService("DataStoreService")
local DataStorage = DataStoreService:GetDataStore("DATASTORE")

local InitiateDataStorage = function(Player)
	if not Player or not Player:IsA("Player") then
		return
	end
	local LeaderStatistics = Instance.new("Folder",Player)
	LeaderStatistics.Name = ("leaderstats");
	local Cash = Instance.new("IntValue",LeaderStatistics)
	Cash.Name = ("Gold");
	local Level = Instance.new("IntValue",LeaderStatistics)
	Level.Name = ("Level");
	local Statistics
	pcall(function()
		Statistics = DataStorage:GetAsync(Player.UserId)
	end)
	if not Statistics then
		Cash.Value = 0
		Level.Value = 0
		print("Saved data is not available, or it doesn't exist yet.")
	else
		Cash.Value = Statistics[1]
		Level.Value = Statistics[2]
	end
end

for _,Player in pairs(Players:GetPlayers()) do
	InitiateDataStorage(Player)
end
Players.PlayerAdded:Connect(InitiateDataStorage)

local SaveData = function(Player)
	if not Player or not Player:IsA("Player") then 
		return
	end
	local Save = {};
	local Success,Returned = pcall(function()
		table.insert(Save,Player.leaderstats.Gold.Value)
		table.insert(Save,Player.leaderstats.Level.Value)
		DataStorage:SetAsync(Player.UserId,Save)
	end)
	if Success then
		print("Save successful!");
	end
end

Players.PlayerRemoving:Connect(SaveData)