I only own the red sizzix. I hadn't used it in years. Then I discovered that the Cuttlebug embossing folders and the nesties both work perfectly in it. I now have about 20 folders and at least 15 sets of nesties.
You will need a Sizzix System Converter if you don't already have one. This is that big magnetic piece that goes up under the top part of the machine. It costs about $15.
I agree with nikki (post #2) about the sandwich for cutting. But I didn't buy a spacer. Instead I cut three pieces of chipboard to 4-1/2 x 6" and taped them together on the sides. This turned out to be just the right width for the spacer. You may have to experiment with what works for you.
As far as the embossing, I have a different method than nikki. After cutting the shape, I make the following sandwich:
nestie, ridge side up
paper that was cut with the die inserted in the nestie
plumbers gasket
piece of fun foam
1 layer of chipboard
The plumber's gasket works perfectly and it only cost 98� at the hardware store. I think it was 6" square so I just trimmed it to fit in the machine. Same for the fun foam (the kind that comes in a sheet in the kid's craft aisle).
Check out
this video on YouTube which shows the nesties being cut and embossed using the red sizzix. Remember though that the presenter is trying to sell you the spacer and embossing mats. You can use substitutes and they work just as well.
Oh... and I know you didn't ask about the Cuttlebug embossing folders, but you don't need any sandwich for that - just the Sizzix system converter. Just put your paper in the folder, put it on the white board and run it through the machine.