Megid and Ilmegid are good for general mobbing. Megid is a lot more useful than Ilmegid in Shironia due to most Shironia mobs having weak points and a ton of HP and/or damage resistance. Ilmegid is expensive and weak, but hits lots of enemies per cast. Uncharged Namegid does about triple a charged Megid's damage so you can use that for single target mobbing. Gimegid and Ramegid are suitable for Zondeel combos. Samegid can be used for single targets like Namegid, but it's mostly restricted to wide enemies like Windira (which it can usually one-two shot).
Light isn't very good for mobbing since fire/ice/lightning/wind all do mobbing better, and light is only effective against darkers. But it's good for Cradle of Darkness since every spawn encounter is mixed. Light has Grants for precisely targeting weak points (mainly useful for Micda because of their shell), Gigrants and Nagrants both combo well with Zondeel (Gigrants kills stuff faster but Nagrants will continue hitting enemies as they spawn, does more damage per use, and costs less PP). Ilgrants can be used similarly to Namegid and usually takes out mobs in one-two hits again. Ragrants is basically restricted to bulky targets at close range, but wipes them out faster than anything else thanks to its ridiculously low charge time when crafted.
Elysion Sazan would be cool, but without that, wind is basically Sazan and Ilzan for mobbing, and Ilzan is really weak. So its only notable mobbing quality is a strong, cheap auto-target tech. Gizan would be cool if its range wasn't so bad, and the damage wasn't concentrated in the final hit (final hit does more damage than the first four combined, 10 * 4 + 60).
Really up to you, but if you're stuck with one tree, I'd suggest going light just for having Ragrants to boss, since Ragrants is one of the best boss killers against darkers.