I have the double blade because I torte every cake that goes out my door. Also because I always use SPS, I need the cake layers to be 7/8" for my four layer tiers. The single blade doesn't *easily* cut under 1". You can do it, but I like easy.
Also tools that I couldn't live without - Magic Line pans and SPS.
Seriously, you will never regret buying great tools.
A plethera of small bowls, extra spoons and spatulas to mix colors.
A nice turntable of course.
A small pointy spatula--just comes in handy.
A one sided cookie sheet to use to hold & place torted cake.
A bench scraper to ice cakes smooth.
Wilton charts for servings and amount of cups of batter--I still use these for every cake I do after these zillion years.
A pearl hat pin or some kind of long pin to puncture sides of cakes so they don't get blow outs under the icing.
A speed rack to contain all the product.
Earlene's website.
Bake-Even strips (or the home-made alternatives)
disposable bags (SO handy over the ones you have to wash)
spatulas - lots and lots in different sizes!
and above all, a positive can-do attitude! Keep practicing and your cakes will get fabulous! The beginning ones may not look pretty, but if you have good recipes, they'll taste great!
A pearl hat pin or some kind of long pin to puncture sides of cakes so they don't get blow outs under the icing.
explain please!! 
that's a new one to me! i've used the pins to do transfers to my icing or fondant, but never heard of stabbing the cake...would love to have details!
starla
Earlene's website.
Yep. It was because of her website that I am where I am today.
Wilton master set of tips and couplers.
Decorating bags (for icing)
Cooling rack - for cookies and cakes
Hat pin trick (I think this is why, anyway! 
)
Blow-outs happen when a iced cake is coming to room temp from the fridge. I think oxygen is released (?) and air gets trapped between the cake and icing.
It almost always happens to me because I always have my cakes in the fridge to set before applying the fondant - but the air gets trapped between the fondant and the crumbcoat. Perhaps misting the crumbcoat with water so the fondant adheres better would work.
Favorite tools:
~ Ditto on the Bake Even strips.
~ My Kitchen Aid hand mixer. It works just as well as a stand mixer, though I can't walk away to let things blend while I prepare something else.
~ Fondant smoother (the cheap one by Wilton)
~ LoRann candy flavoring oils!!
~ Luster dusts, pearl dusts, sparkle dusts... (OK, not a must have, but really adds to a cake).
~ The BEST tool ever... CakeCentral.com 
www.earlenescakes.com
i use her site for my servings...down on the bottom right, there will be a link to "serving sizes". i also use her kahlua fudge cake recipe from the "recipes" link.
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