You're in tier 3 now so all 204 gear is available. LMG'S are currently very strong in the game so I'd personally buy the Pakhan if you're still struggling for a decent 204 weapon (I assume the talents are the same a tier down, destructive and ferocious is 2 I remember in tier 4).
You'll soon build the credits back up, I grinded for acouple of hours earlier and went from 1.2mil to just under 5mil selling everything I got, not deconstructing it.
Your gear score doesn't denote what you can and can not buy like your player level when going 1-30, if you were in a tier lower the pakhan would still be available to buy but at that tiers gear score.
The weapons are more balanced in the latest patch but there are some variants that have higher damage, like a base M60, Black Market M60 and Military M60. The Police M4 assault rife and MP5 SMG are acouple worth looking out for if you come across them. When it comes to weapon mods, headshot damage on the suppressor and optic, Mag size on the clip and stability/accuracy on the grip for weapons that recoil badly.
To toughen you up abit roll armour on gear where possible: Chest piece, backpack, knee pads and holster
