Gold for Next Year's Halloween Event
If you're a long term gold strategist such as myself, you'll start stocking up on "Hallowed Wands" now for next years Hallow's End event.
On the opening day, transformations sell for over 25G a piece so you can quickly make a lot of gold on the first day before anyone else collects Wands from the Innkeeper Trick-or-Treat bags.
The next day, prices will drop to 15G, then 10G, then 5G, etc. So you'll want to advertise Achievement transformations as much as possible on the first day of Hallow's End next year.
The cooldown on "Trick-or-Treat" is 1 hour whether you're logged in or not - so just rotate through all of your realm characters and try to collect as many Treat Bags/Wands as possible and just store them in your bank. All of the other Hallow's End items pretty much expire and disappear.
With Christmas coming up, you'll also want to fill up a couple (personal) Guild Bank Tabs with the Gingerbread Cookie and Egg Nog recipes. Wait a few months after Christmas, and you can re-sell those recipes for 25G a piece or more (and there's almost no competition in Jun/Jul/Aug).