Maggie's main gun is the TAG-standard Multi HMG, giving a choice between Burst 4 Shock or Armour Piercing ammo or Burst one Explosive or Stun ammo. At BS14, this is arguably Haqqislam's best unit for winning a fair fight between 16" and 32". With the BS and maneuverability of a TAG this HMG remains effective against weaker targets even at ranges where its not getting a bonus to hit.
Depending on the profile, a Maghariba's secondary weapon is either a Heavy Flamethrower or a pair of Heavy Pistols. The pistols give a more effective Face To Face weapon for short ranges. Alternatively the flamethrower gives more versatility, able to Intuitive Attack markers and trade guaranteed hits with opponents (relying on its high armour to survive).
And lastly the pilot wields a shotgun, making them reasonably dangerous at short range despite unremarkable stats. Voluntarily dismounting to attack is unlikely to be worthwhile because of the risk to the pilot, but once the TAG's crippled the pilot is likely to be well positioned to take revenge (because in my experience most TAGs die at close range).
BS14 Explosive ammo, Armour 8 plus cover, three Structure and the option of a flamethrower mean that little can attack a Maghariba with any certainty of victory.
You can vault over most terrain, and shoot while at the top of the movement. You'll forfeit cover, but that's often worth it for the unexpected lines of sight.
If your Maghariba and nearby engineer both go down, you can potentially have the pilot leave the TAG, Paramedic the engineer, who then repairs the TAG, then the pilot remounts.
Trap Maggie in hacking range.
Get a melee expert into combat.
Possess Maggie and leave something in base contact so it's in melee once the TAG is reclaimed by its owner.
Win a Face To Face or two using a high damage weapon such as linked Missile Launcher.
Catch it out of cover and keep shooting: TAGs are tough, but far from invincible.
You need enough board control to prevent Maggie being outmanouvered or engaged in melee. Fortunately Ghazi Muttiwiah are amazing at the latter.
Other useful support is enough hacking to preemptively kill enemy hackers or re-possess your TAG, a Fiday or similar to eliminate enemies which can realistically threaten the TAG, a Djanbazan covering in front of it to prevent enemies approaching under smoke cover, an Engineer for repairs, and a melee expert to remove anything which manages to engage the TAG.
Active Turn Role
Kill any exposed target it's likely to beat, then take up a position to watch a significant section of the table while not immediately at risk from anything which can reliably damage it.