@OlBoy88 There's a couple things to consider when sifting through the info provided above 1.) are you able to use the weapon/weapon type the as effectively as the person offering the advice and 2.) weapons within a category can have a wide range of stats and need a varying set of mods.
To my first point, I'm not always the best shot so I tend to mod my weapons to compensate for both the weapon and my deficiencies. Bonuses to DMG and crit DMG are nice, but you need to make sure that you're hitting for those to be useful. When you "spray and pray" you might look for increased ammo and reload speed so you can reload less often and do it faster. If I'm able to reliably connect on my shots, I'll go for mods to buff damage, ammo capacity and range.
For my second point, you can look at some of the "blanket" suggestions as to how you mod your guns, but you need to look at the stats of the weapons within that group and even sometimes within the same weapon. I used to run a lightweight M4 and that AR needs mods to increase stability (it climbs up targets) and DMG, because it doesn't hit hard. My black markert AK hits hard but needed horizontal and standard stability mods to keep it from jumping everywhere. Since it does a lot of damage, I was then able to supplement it with crit chance and DMG mods. Also, some LMGs have small clips (AR size) and reload fast so increased clip size mods and stability mods are good while others have large clips and reload slow so increased reload speed and stability mods are good.
So here's what I tend to do with my weapons:
AR: muzzles - crit chance & crit DMG, grips - stability (including horizontal), clips - weapon DMG
SMG: optics - optimal range, muzzles - crit chance & crit DMG
LMG: mags - reload speed, grips - stability & accuracy, muzzle - accuracy
Shotty: optics - optimal range, mags - reload speed & ammo capacity
Sniper: optics - headshot DMG, muzzle - crit chance & crit DMG
Note: I added the mod types after rereading the original post. I'm looking for info that lists what type of mods (muzzle, optics, grip, etc) can offer what benefits to post with this.