Storing a lot of data all at once in a simple manor?

You can create an entire player's save in a model, like I've done. Whenever you want to add something new, just add another instance value in the model. (Like number value, bool value, stringvalue, etc)

Create the model with everything you want to save and parent it to the script. In my example, i named my model "PlayerSave"

In explorer, it would look like this:

ServerScriptService:
	script
		PlayerSave
			ValueOne
			ValueTwo
			ValueThree

local PlayerSavedData = game:GetService('DataStoreService'):GetDataStore("TEST")

game.Players.PlayerAdded:connect(function(player) --When the player joins
	repeat wait() until script.PlayerSave --wait until the model is actually loaded
	local save = script.PlayerSave:Clone()--Create the PlayerSave Values
	save.Parent = player --Put the model of values inside the player
end)

Then, make the table for everything in your model you made, you will have to add to this table if you added another value instance to your model.

function PlayerDataTable(player) --Name of your table (it can be anything)
    local savevalues = { --in this example, i have 3 values. you can add more, just add to the list when you want.
		ValueOne = player.PlayerSave.ValueOne.Value,
       	 	ValueTwo = player.PlayerSave.ValueTwo.Value,
        	ValueThree = player.PlayerSave.ValueThree.Value
    }
	return savevalues
end

Then, you're going to add the player's save onto them when they join.

game.Players.PlayerAdded:connect(function(player)
	repeat wait() until player.Character
	repeat wait() until player:FindFirstChild("PlayerSave") --wait until the player has their save model
	local data = PlayerDataTable(player)
	local playerkey = "player-"..player.userId --the individual player themselves
	local SaveFiles = PlayerSavedData:GetAsync(playerkey) --get the player's save
		if SaveFiles==nil then
			print("player has no save yet") --if the player is new
		else --if the player has a save
			player.PlayerSave.ValueOne.Value = SaveFiles.ValueOne
			player.PlayerSave.ValueTwo.Value = SaveFiles.ValueTwo
			player.PlayerSave.ValueThree.Value = SaveFiles.ValueThree --Puts the save file inside each value. Add to this list when you want to add another value to save.
end)

Saving just works the same way, but add the table.

function SaveData(player)
	local playerkey = "player-"..player.userId --individual user
	local data = PlayerDataTable(player) --the table
	PlayerSavedData:SetAsync(playerkey,data) --save the table to the user
end

Save the entire player's save when they leave the game.

game.Players.PlayerRemoving:Connect(SaveData)