In lane, she's mostly Q spam. Charm is mana inefficient and rarely worth using unless a fight gets messy. Either way, with the terrible base stats of a mage she's usually best off firing Q and running in trades.
After you leave lane, you poke with Q, you fire charm when you're confident it will hit and if it does you can use q + w as well. It's mostly used as a pick ability, from bushes or what not. For waveclear, if you have the ap you can q the wave and then w the melee minions. Otherwise 2 Qs are needed. If you're diving in on someone, R in and use W, but expect an opponent to get evasive. They expect the charm, and you often dance with them a little before firing it and Q. Never dive someone you don't already hold the upper hand against.