The jann: weakest of the genies and not associated with a particular element. Despite being only one HD below the djinn, the jann's CR is half theirs. Does this affect their LA? Keep reading!
Jann share a lot of traits with the other genies: good stats (they even surpass efreeti in one), a fly speed (albeit a pretty slow one), free Improved Initiative, telepathy, and Plane Shift (no complaints here). Just like efreeti, they can change someone's size, though once more they're probably the best target for that.
SLA's vary greatly in use. Invisibility is nice (Move Silently is on their skill list!) but Speak With Animals is long outdated. Create Food and Water isn't that great (though note that jann do need to eat). Ethereal Jaunt for an hour per day, however, is just great.
Finally, there's the weird 'Elemental Endurance', which makes jann take damage for spending too much time away from the material plane. Then again; a few charges from a wand of lesser vigor take care of most of it, assuming long-term missions to the elemental planes are even a thing in your campaign.
So what LA to give? Plane Shift is something I'm not sure should be available at this low a level: even jaunters don't have it yet. Combined with a pretty good chassis and some general open tricks, I think +1 LA is warranted here.