Most people like to power level through this stage. I don't, but that makes me kinda unusual. Power levelling in this game consists of a party with up to seven people at similar levels and a lvl 50 mage (THM, usually). Mage aggros everything in the area and then gets booted from the party. Once he's out of the party, he AoE's all the mobs and the party gets all the XP. The people being power levelled pretty much just stands around. I find this very lame, but it does level you *very* fast. Not only does this leach away all the people you might have partied with, it means that people go from 15 to 35 in a few days, so there just plain aren't that many people at your level.
Now, let's talk about what you can do while *not* power levelling. You can continue solo grinding and doing leves; unlike FFXI, this will get you advancing at a good rate. If you can join a party, it will be faster, so looking for one isn't a bad idea; just don't be surprised if you can't find one. My personal preferences are party is better than soloing is better than power levelling, but like I said, I'm different. Incidentally, go to
www.mooglebox.com and look at their mob location tool (under "Other Stuff"). It's a great way to find grindable camps.
Shposhae does have nice level 15 gear in it, but Shposhae is designed to be run by a full party around level 15. And it would rock if people actually did that. To get at the best loot, you have to figure out how some things work that are very nicely thought out (and will get you killed at the intended level if they take you by surprise). Alas, I've never gotten a Shposhae party, and I don't know anybody who has. When I go there on occasion to farm stuff, it's empty.