How to Level X weapons in multiplayer?

@croSSeduP 

I'll address your subject thread in a bit.  But first, I want to get to the elephant in the room...

"This can only be because they have level X weapons"

NO!

The single most important factor in the game is by far, YOU, the player.  I have a maxed manifest, and I still am not good in Platinum.  There are players who can run rings around me with the worst kits and lower rated weapons.  OTOH, there are players I can triple the score of using mid-tier weapons.  I cannot stress this enough.  So, my suggestions are:

Do a lot of reading in the ME Co-op Reddit group and/or the New BSN (not associated with Bioware).  Especially:

Reddit Coop college 

ME3 MP Resource Library 

I looked at some of your builds.  They are ... interesting.  You spend (IMHO) far too many points on fitness, and are not "properly" speccing some of the most useful powers in the game.  Yes, you want to stay alive, but you also want to help the team by doing damage and crowd control.  You should always take advantage of debufing options (Prox mine 20% enemy dmg), stunning is not to be overlooked (radius on most powers, chain on Overload).  Almost always take the rank that gives a power a buff vs. armor (the warp spec you have on your HM Sentinel is how it should always be).  Know which rank 6 options are musts, which are a waste of points.

Consumables are very important, but you seem to be using those.  Knowing which works best with what weapon is key (and understanding their glitches/exploits, if you need help).  Hint: incendiary ammo is ungodly on certain weapons (Reegar....) or combined with powers (Warp...)

Okay, as to your thread subject:

There are only two ways: keep playing (and if you are dying that quickly on Plat, drop to Gold) to get credits.  Or use a cheat to get credits (which obviously, I can't post here).  I strongly suggest doing it the right way.  To me, part of the fun is the joy of getting a UR (after the anguish of a 20+ losing streak).

Any of the premium packs (PSP, Reserve Pack, Arsenal Pack) have exactly the same chance at a UR (7.5% for each of the two Gold slots, so 15% for the pack per 99K credits).

The SP pack has one of those 7.5% slots for 60K, so less UR's/credit, but it gives some stuff you still need at better odds (Gold weapon mods).

I'd suggest you still get PSP or RP or SP since there's a few top-tier gold characters you still have to unlock (the AP doesn't drop characters).  I'm talking Ghost, Alliance, Geth, Huntress Infiltrators, plus M Quarian Engie.

Last:

Some of the Gold weapons are as good, or even far better, than most of the UR's.  The Reegar is the single most OP gun in the game (but has obvious limitations).  Some players are godly with the Acolyte.  And most "pros" absolutely love the Claymore (you have to learn "reload cancelling" to make it, and many other single-shot weapons, most effective).

[edit] In reading my first reply, I was for some reason translating "level X" as "UR".  But 100% of what I said holds, with one modification:

For Gold Weapons (to get them to X), Arsenal Packs are the best choice.  PSP/AP/RP give same max gold items/credit, but AP's give only weapons, RP's give only characters, and PSP's are balanced to both.

Having said that, I'd recommend you get PSP's, so you can get some of those missing uber-powerful Infiltrators currently locked.  And maybe some SP's to fill out your weapon mods.  I consider leveling weapon mods to be more important that just a few more levels in a Gold gun you have;

Other best Gold weapons besides the ones I previously listed: Arc Pistol, Collector SR, and Piranha.

Also, getting to Level X is only an incremental improvement. Generally 25% more dmg, 25% more ammo, and somewhat lighter weight, compared to L1.  So each level is just ~2.5% better, though not to be sneezed at.  In a few guns, it also provides other perks like better stability (Hurricane, Typhoon, I'm looking at you)..

There's no right or one way to spend points.  I just noticed you tend to have full 6 on Fitness.  Sometimes I have 6, sometimes 4, sometimes 3, rarely 5 or 0 (though some confident players go with 0 and probably rely on Cyclonics, defensive abilities, and properly timed use of Ops packs to stay alive).

For what is called the racial passive (#5) it depends. But virtually NEVER is 6a (reduced gun encumberance) chosen over 6b (gun dmg).  Base Turians and Drell have awesome passives.  I love the extra Turian stability, but note it is bugged, only works if you host, or if you are NOT the last person to join the lobby.  A royal pain that one is.

Powers: sometimes I skip one of them (the Krogan Vanguard skipping Shockwave is the norm, the Human "Novaguard" build also forgoes Shockwave).  Lots of people only spec Pull to 3. Some powers have weak or buggy rank 6, so maybe better to put those to 3 ranks in Fitness, etc.

That's the beauty of the game.  There are many ways to build a character to suit your play style or whim.  While none is "right", there certainly some that are demonstrably more powerful, or OTOH, far less optimal.

Take a look at Big Bad List of Builds and you'll see a diversity of builds.

BTW, do make use of Kalence to explore those builds and yours (the other link to "Narida" is older and not as up to date).

Or if you see some guy who played an awesome game with you has their N7HQ visible, and check out their build.

But more important than any of that is to know the games mechanics, and general strategies (combos, especially Biotic, with a very few exceptions are much more important than the ability dmg component.  So buffing combo dmg is generally much more important than the racial passive (which only buffs non-combo dmg).

And situational awareness (Geth Scanner is almost cheating).  And fast thinking, trained muscle memory...