Hwo should I approach making and inventory system?

http://tinypic.com/r/rgz2o7/9 is the image of my explorer.

So Am I starting off alright? I don't know how I'm going to approach and start this. My goal is to be able to script a working inventory system. I want to only be able to have two items in hand or default backpack and the rest will be in the GUI inventory. I was thinking maybe have folders for each type of item and each item inside. Each folder containing the image the data and the item itself? And maybe somehow I can work that out. I really dont know how to approach this. I am in fact experienced with scripting too. I'm also almost losing my scope or main idea in which is to make a working basic system without much detail like the data of weapon image etc. I want to be able to put gear in gui inventory and be able to take out or interact in a way. Should i start with being able to get an item by pressing a key and putting it in my default backpack? Please do give me tips I'm not asking for script I just want a boost on what I should focus on doing.

The only code I got workign so far was being able to click on image in inventory nand have output print it works

script.Parent.MouseButton1Click:connect(function()
	print ("itworks")
end)

With my old system I made buttons and put a string value in the button object and then made a script for when you pick up an item it checks each item

local player = game.Players.localPlayer
local gui = player.PlayerGui.Inventory.Frame

if gui.Item1:FindFirstChild("Item").Value == "" then
gui.Item1:FindFirstChild("Item").Value = "ItemNameHere"
elseif gui.Item2:FindFirstChild("Item").Value == "" then
gui.Item2:FindFirstChild("Item").Value = "ItemNameHere"

pretty much the basic script you could also put a numbervalue for stack size say you pick up 5 rocks it'll have a number value for stack size says five

gui.Item1:FindFirstChild("Item").Value = "Rock"
gui.Item1:FindFirstChild("StackSize").Value = 5

for dropping an item you could do

script.Parent.MouseButton1Down:connect(function(click)
local c = game.Lighting:FindFirstChild(gui.Item1.Item.Value):Clone()
c.Parent = game.Workspace
c.CFrame = CFrame.new(player.Character:FindFirstChild("Right leg").CFrame)
c:FindFirstChild("StackSize").Value = gui.Item1:FindFirstChild("StackSize").Value
gui.Item1:FindFirstChild("Item").Value = ""

end)

pretty much the main jist of how one works message me on roblox if you want more help add me too I'm always willing to help

alextheotaku (got a name change)

Heres a working uncopylocked inventory system I just made for you :)

http://www.roblox.com/games/329189941/Inventory-System-Uncopylocked

very easy to use and edit I hope you enjoy stacksize isn't 100% working yet but you should be able to edit it