[Norfleet]

I'd go with Conjuration. As you yourself noted, your gem income remains presently anemic....this isn't going to improve much unless you start doing some more band-scanning for sites. At the rather poor mage-time ratios for vinecreature summonings, plus that it'll likely take you a turn or two to even get set up, then move all your newly summoned creatures to the front, it'll be at least a dozen turns or so before they start showing up in useful quantities. Better to work on getting the gem machine rolling, which will greatly expand your future options.