It's worth grinding the horn to sell if you're after Gil, at least on light. If after the event you grind the scrips for it, you would get about 200-300k more by instead buying pots of dye at 100 scrips each and selling it at 5 pots at a time for the same number of scrips.
Just horde gold saucer coupons, especially if you're new. One day something cool comes up for 4mil mgp and then another thing and another - all that gil won't help you.
I would like to add a sidenote, for people who are in earlier content and/or on the free trial (like me)- The most efficient run I have found so far is the Alexander - Fist of the Father raid. As a WHM running the raid with a party of blue mages we got the runs down to about 2mins and 30seconds per run. At 2 tomes per run we were making 50+ tomes per hour. And then even when the part wasn't entirely blue mages and just a variety of normal combat classes, the run would still only take anywhere between 3-4mins and result in making about 20+ tomes per hour. So for those people looking for a dedicated route to farm of easily accessible content, this was the ticket.
