You can probably get by without soh for now if you want, your hp is solid enough to probably cure off the damage.
I'd probably take electro next and then scorching after, could probably work on soh after that.
Light wave can be good in places like fiesta but the aoe is awkward since it's sort of like a cone and the waves can be a bit picky about what they want to hit at times. I'd say hold off on this, the ma requirements for later fiestas are sort of steep for electro, so light wave can help there.
For leveling, I'd suggest floor 30 of chaos tower based on your ma. This is a pretty helpful guide line for the areas you might want to train in: /forum/magic-type/84...ma-needed.html