Shadow Shelgon

Dragon Breath + Flamethrower and Twister

Dragon Breath is the recommended fast move, with high damage output backed by STAB. Ember sports the average 3.0 DPT (Damage Per Turn) and 3.0 EPT (Energy Per Turn), which is inferior stat-wise but its typing gives it a niche. 

Twister offers horrible damage output for its energy cost, but STAB makes it a little less miserable to use, in addition to it being cheaper in energy than Shelgon's other charge moves. Flamethrower offers some extra coverage, in particular against Shelgon's weakness to Ice-types and common Steel-types. Dragon Pulse is significantly more powerful than Twister, but high demands for energy makes it very cumbersome to use.