Alchemists do not have an all around attack like most classes. They start out with a spell called Poison Shot that at a high level (about level 6), can kill almost all small enemies without the, getting to you. It does 25 to 35 damage and does not use a lot of energy. You can cast it very fast to surround yourself in clouds of poison that will kill everything near you.

When you are high enough level to get "Fire Bomb", get it and do nothing but upgrade it. Over time, the bomb will explode instantly after you drop it and do over 300 damage.