Leveling a Shadow Chaser is just slow, period, at least when compared to every other class. You can certainly do Shadow Spell all the way to 150, and in the later levels Shadow Spell isn't half bad for leveling.
However, I wouldn't recommend leveling with Storm Gust unless you are fighting boss flagged monsters like Kasa. Normal monsters get knocked back and frozen by the skill, and it takes forever to kill a single monster that normally would only take a few seconds to kill. Your main skill is going to be Meteor Storm. Use it on pretty much everything except fire property monsters.
As for leveling spots, I don't really recommend Nogg Road. The reason for this is because it's extremely mobby down there. Most other classes have burst damage attacks that can quickly kill groups of monsters, which is why it's good for them, but Shadow Spell Chasers don't. Shadow Spell is basically damage over time, and you have to be careful about how many monsters you have on you at one time, especially if your MATK isn't too high. My suggestion would be to do the Kiel Hyre quest so that you can level in the Robot Factory. The monsters there give pretty decent exp and you don't have to worry about getting completely overrun, though you'll want some kind of fire armor to protect yourself from the little bomb guys that float around down there.
Another place that might not be too bad is Ice Dungeon in the lower levels if you have an unfrozen armor.