I want to order a dummy cake but the site I went to
d a l l a s f o a m . c o m , has so many diameters and heights to choose from I don't know where to begin.
I guess what I am looking for is a 3 tiered round cake to practice wedding cakes etc, but also party/special occasion cakes.
I like the looks of those extra tall stacked cakes, but to start out with I want a basic "set".
Any suggestions?

You could try their store on ebay. I agree that their site is very difficult to navigate (the first time I ordered from there I mistakenly ordered dummies that were completely different from what I wanted!). Their store on ebay has a clear photo of exactly what you'll be ordering and it's much easier to check out. There's also other stores on ebay that sell cake dummies if you do a search.

Personally I would get at least a 6,8,10,and 14. That way you can go 6,8,10 for a 2" difference between tiers or you can do 6,10,14 for a 4" difference between tiers. You should definately get the 4" tall tiers since that is usually the standard height.

Thanks! That helps clarify it better for me.