You buy ...
a huge multicannon,
a large multicannon,
a large multicannon,
a large multicannon,
a medium multicannon,
a medium multicannon,
a small multicannon,
and
a small multicannon.
Believe me, firing eight (fixed) multicannons pushes the legal limits of fun that's permitted to have. Then you overcharge the frick outta them and slap some corrosive on the huge one whereas the others are all incendiary. Also get that charge enchanced distro and G5 DDs with drag drives.
Stacks as many boosters as possible. Then you want to deactivate the throttle limiter in your ship's board computer. Many manufacturers use this for civilian vessels but with this limiter, also know as flight assist, disabled you will be much more manouverable in this giant space brick with alotta multicannons to the face.
Also, copyright goes to Rinzler o7o7o7.