The low level caravans give less seals then the high level solo leves, so if you can do the high level leves I'd do those. If you shout in town you might be able to get a group going for caravans, the high level one can give 1/3 more to double the amount of seals as solo leves so are more worth it if you get a group together. The Ul'dah one seems to be doable with 4 people, 5 is an easy win. You can switch to a crafting/gathering class right before the end to get XP on them, so it might convince others to join.