It's pretty simple.
Boil down your key actions to these tips and rules on the front.
1. Don't be the POINT-MAN (GUY IN THE FRONT LEADING THE PUSH), no, your SG isn't going to kill that ravager without help.
I remember one round I unloaded 20 bursts with armor shredding into a ravager and it did not die or feel threatened enough to not kill me.
2. Take BINOCULARS, laser designators, regular or rangefinders. Staying behind the pointman means you don't always know what to expect even with the SG MD. Use your binoculars when you feel the urge to to scope out what's coming and to get to the best position before the xeno does or moves in to attack.
3. Bring at least one high-capacity battery or better
(optional)
try to get a medkit pouch and medkit to fill with injectors and bandages rather than being limited to just two first-aid pouches.
Bring a M44 with enough heavy ammo, a B8 scope, Recoil Compensator and optionally a Laser Sight. These attachments allow you to shoot one handed with less recoil, and going through all regular marines and Almayer crew. Heavy ammo doesn't apply an ability lock or daze though, it will however flicker stun all T1s in most cases and some T2s (lurker, spitter, burrower) at close range, this is useful when you are getting chased and need to run, where wielding your SG and firing wouldn't do much and get you killed.