There is actually no need to get Limited Edition stuffs if you aren't able to do so. For me, buying a simple CD so that I can listen to and support ayu is enough, I don't need to fork out cash I don't have to purchase the same thing in USB form, just because it's "limited" and "special". What's important at the end of the day is the music, right?
And no need to worry about getting the album the moment it is released. If you want to listen to it over X'mas, AHS Downloads is your best friend. Wait till you're financially more able, then get the CD to show support. ayu (or avex) will always be there to sell you a copy, be it on 22nd Dec 2010, or in 2015.