I have a minimum order, so my smallest 2 tier is $118, decorated or not. Fully decorated like the picture would be $126, and you'll spend more than $8 at Michaels. So, I want you to be prepared to hear a much higher price than you at expecting for this "plain" cake. If you have a tiny budget your best bet is to make it yourself. If you can't bake, the store brand mixes are still fool proof, follow the directions but add an egg. Use whatever pans you have, and trim to the size needed. Make American buttercream, a quadruple batch is about $12. The mixes would be about 10. A roll of Viva to smooth with is $2. Use a butter knife and credit card to smooth it. I think the primary colors fondant is $20. Start with yellow and add a smudge of the red fodant at a time to make orange.
Someone on a computer who is familiar with the site can direct you to some great threads that will tell you every thing you need to know. JanH? Hello? She is fabulous at finding links.
I warn you that cake decorating can get in your blood, and is a VERY EXPENSIVE hobby;-) and is also a lot harder than it looks!
Maybe you can cut the budget somewhere else, if the cake is that important? Just saying.