Ok...
Let me run through this here quick.
Spirit and You: The plight of the caster pre wotlk.
Spirit was utterly useless basically except for more mana back when you finally had to pop innervate. When the 3.0 patch dropped the Imp. Moonkin talent was added basically making spirit a worthwhile stat to be stacking and looking for as a boomkin. When fully talented it's will add 15% of your spirit into spell damage. Now being your level this isn't your biggest thing you'd want to look for, but it really does help with the extra mana regen you'll need at a lower level. Also if you're talented into Imp Moonkin you'll also receive a haste bonus which in itself is very very nice. So for now spirit should be the least of your worries until you reach Outlands where spirit/spell power gear becomes more and more abundant.
Once you do hit Northrend you'll find all sorts of fun gear to replace the quested/instanced items you got in outlands. Now me on a personal basis was lucky enough to raid the t6 raids so I had a few pieces of balance gear that already had spirit, and things that I had supplemented when I was resto pre 3.0 that had much spirit on it as well.
The whole trick to leveling as balance is if you aren't full of items that add tons of crit, which is a huge HUGE way to keep yourself going, especially balance. You're going to end up wanting to stack tons and tons of spell power and int. My reasoning behind it is this.
More int = more crit. Now as you level obviously it begins to scale down and that is a given. But more int also means more mana for quick leveling/questing. The more spell power you have is going to correlate directly to the damage you're pushing out.
But if all this is confusing and what not. I still believe that balance is more of an art form than a simple walk in the park. And if you want quick results, you're best is most likely going to be in the feral tree. There is more of an abundance of feral gear in outlands when you reach that than there is caster gear that isnt cloth.
In my honest opinion. Try both trees out to see what suits you best. It isn't hard to build greens for each set, and money shouldn't be an issue once you hit outlands.