Practicing!

Welcome to the addiction!  I didn't do much practicing.  I just made cookies for friends and small orders and learned along the way.  My cookies are about 1/4 inch thick and with the icing it makes it about 1/3 to 1/2 inch in places which seems to be the norm or it can be too sweet and hard to eat. 

Practice makes perfect with baking or anything else for that matter. As far as ingredients go, I think they're relatively inexpensive compared to others. Just imagine if you were a chef practicing how to make Beef Wellington or Lobster Newburg! My best recommendation is to pace yourself so the costs don't overwhelm you. You could also try decorating on cardboard, though that's not quite the same experience as decorating on the real thing - and then you can't eat your mistakes!

I would suggest practicing on parchment paper...after the icing dries completely, you can literally dump all of the icing into the garbage and use the parchment again for more practice...

That's how I've had my helpers practice.

And yes, welcome to the addiction!!

I practice piping on an old wooden chopping board as it absorbs the moisture from the icing similarly to the top of a cookie. I also keep extras, or mistakes, for ages, and use them to practice stuff - today I used a three month old cookie to see what the Dr Ietker silver spray looked like, before using it on the fresh cookies.

I have also had people recommend using store-bought shortbread rounds or other cookies with a flat bottom, turning them upside down to practice outline, flood, and decorating.  I never tried that, but think it's a great idea.  That way you can at least eat the practice cookie. (I also save "old" cookies to practice on - they are in a plastic container clearly marked "do not eat - old cookies" so my kids don't think they can get at them!)

You could decorate graham crackers.

How about using Ritz Crackers?  They aren't completely smooth but would work I think.  I have used plates, cutting boards, and on occasion, the counter 

Ali's Sweet Tooth decorated a bunch of Ritz crackers recently and they looked great! Or try graham crackers or any flat store-bought cookie. 

While I don't think the cost of baking and decorating sugar cookies is very high, the time investment IS. I'd say go ahead and decorate your heart out and don't worry about the cost. My problem when I started out was having all those cookies and no desire to eat them all. So I took all my practice cookies to work, and my co-workers never once complained about what they looked like!

buy some of these to practice! http://www.karenscookies.net/N...e-Cookie_p_2009.html

YES! Buy the Notta Cookie, which just came out. It's helpful for practicing stenciling too.