I have four different movesets for him. One is a supporter moveset while the other three are special sweeping movesets.
Ability: magic guard (ability turns to trace if you decide to use mega alakazam for this set.)
EVs: 252 speed, 252hp, 4 hp
Item: Leftovers/ Alakazite/ light clay
Wonder room: switches the defense and special defense stats for all Pokemon for 5 turns
Reflect: Halves physical damage for 5 turns (8 with light clay)
Light screen: Halves special damage (8 with light clay)
Recover: restores 50% of your entire hp.
Strategy: This set is pretty good if ya ask me. Here's how it goes. depending on what kind of sweeper your up against(physical or special) or depending on how bulky the Pokemon is if its more defensive or more special defensive, you will use wonder room. reflect and light screen are for decreasing the damage you take and recover is for restoring the damage you lost. For single battles and rotation battles you don't want to keep Alakazam in forever so its best after setting up and gaining back some of your lost damage that you switch.
Role: Typical special sweeper
Ability:Magic bounce (Trace if you mega evolve it afterwards)
EVs: 252sp atk, 252speed, 4 hp
Psychic/Psyshock: psychic for more damage and 10% chance to lower special defense or psyshock if ya wanna do physical damage.
Dazzling gleam/signal beam: Dazzling gleam does slightly more damage and is a fairy type move but signal beam has a 10% chance to confuse and is bug type (either way both moves cover dark types)
Shadow ball: covers ghost types and 20% chance to lower special defense
Calm mind: Raises special attack and special defense by one
Role: Fast specs
Ability: Magic guard
EVs: 252Sp atk, 252speed, 4hp
Item: Choice specs
Dazzling gleam/signal beam
Trick/energy ball: Trick to put your opponents Pokemon at a disadvantage or energy ball for extra coverage.
Role: Stab Sweeper
Ability: magic bounce (Trace if you mega evolve)
EVs: 252sp atk, 252 speed, 4 hp
item: Twisted spoon/Alakazite/leftovers
strategy: Perhaps I should explain. Psychic is used against Pokemon with less special defense and psyshock is used against Pokemon with less defense. Wonder room is for protection purposes in case you are up against a strong physical sweeper. Calm mind is self explanatory.