I'm going to have to say suck it up and buy them.
You don't need them to level, you can go back once you're already 90 and have more viable methods of income.
I don't mean to come off as rude, but I think farming the scrolls themselves is a very, very bad idea. The drop rate is simply abysmal. 1.5% off of mobs that respawn every 16%, less than 10% off of NMs that spawn every few hours...
Couple this with the fact that every other do-it-yourself person is going to be trying the exact same strategy, and statistically, you're going to spend hours and hours on every spell. You'll be lucky to snag one scroll a day working all day. It's just bad business.
I tried to farm flood for a couple hours, without much luck. Then I did a quick AH-scan for an 'expensive' NM drop in abyssea. Brought a friend, bought two pop items for 1k each, came back out with 360k~ worth the loot. Took maybe 30 minutes, all told.
The scroll of flood only costs 300k. See where I'm going with this? You will spend an order of magnitude longer farming scrolls and getting frustrated at the low drop rates as you will just sucking it up and blowing away whatever reserves of gil you've obtained, cashing in your dominion notes, cruor, etc.. or farming gil in abyssea via goldboxes or NMs.
tl;dr: It is much, much easier to get the gil than the scrolls. I'd suggest skipping what you don't need until 90 and then going back to fill in all the gaps, if it's your first job. New 90's are always gimpy for a while.
If you're like many and love the feeling of 'saving money' then by all means farm the scrolls, but realize that your time is worth money, as you could be using your time to -make- money, and you're losing way more time farming the scrolls. Opportunity cost, and all that jazz.
1.5% drop rate means exactly what it says on the tin. Not "1.5% but for me the stars will align". But 1.5% as in "You'll have to kill about 66~ enemies on average to get the scroll. It may drop on the first, or you may not have it after 200 kills. And if you don't, you will be absolutely no closer to getting it than when you started."
Edit: If theres anything you can skip for a while, it's ancient magics. They're terribly slow, terribly inefficient, and all around awful spells except for yellow !! which is not important until you're 90 anyway.
Unless you want to solo pets for EXP, but even then, so long as you have -some- ancient magic you will be fine.
Edited, Jun 27th 2011 7:41pm by ItsAMyri