Well at lvl 12 you don't really have any sort of rotation. Just spam trash and discharge and shock (once you have points in induction). When maul procs, you can use electrocute to get behind enemies (in pve shock works too vs standard/weak mobs).
Below is the baseline lvl 50 deception rotation, so you can just keep adding these abilities to your rotation when they become available:
overcharge saber*
relic*
spike (breaks stealth)
force slow
voltaic slash (trash in this place before you get VS)
voltaic slash
recklessness (this is assassin's best offensive ability, it is what really kills people)*
shock (uses 1st charge of recklessness)
discharge (uses 2nd charge of recklessness)
assassinate (if the enemy has over 30% hp at this point, then start new rotation/improvise until he/she is under 30%)
*=optional, depending on cooldown status
Maul can be used on proc, use low slash or electrocute to buy time to manouver yourself into position to stab. If spike procs maul boost, then it is perfectly fine to maul while the enemy is on the ground before starting the actual rotation.