You don't need other pads other than you multipurpose platform AND the tan embossing mat that was posted about so you can get the embossed edges of spellbinders. You can find the tan mat with the spellbinder section of you local box store generally or on here as well!
The metal shim is nice for a die with lots of small cuts. You don't have to have one, but it is nice. I got got mine last month and makes those die much much easier!