I'm taking this experience from another mod but since there's been no reply it may be similar. The expedition may cost less hammers than an actual settler. Trackers can fly if they are upgraded from warriors who are already mounted. When you want to create a city, and there is an expedition built, there should be some kind of make city button on the recon unit. This will found the city and wont consume the unit. Also, explorer/caravel line can summon shore parties who can also use the ability. You can only have one expedition prepared at any given time, but if you're really in a hurry you can build as many settlers as you like too. Again this is from my experience in wildmana instead, so there may be some differences.