Greetings, from lv 1-29, using 2 x LMGs (for the suppression effect), and using gear that has Firearms is the way to breeze through the game without any issues.
Equip a Healing Station and the Gun Turret (change to the Scan one when available) for extra help & to serve as distractions.
Try to put the weapon Talent Predatory in the weapon so you can get healed after every kill, and try to put Enemy Armor Damage % on every gear that allows you to do so.
Once you get to lv 30 and World Tier 5, it really depends of the Build type that you can to create. Skill Builds for Sticky bombs, Gun Turrent, Seeker Mines, Flame Turret, or if you want to just pew-pew your way out, you can create other weapon specific builds.
I can post you the preferred stats of each one of the WT5 lv 30 builds, but this post will become a book, so you are looking for an specific “play-style”, ask away.
You can check on Youtube for PvE builds like Classified Tactician 1.8.3, Classified DF3 1.8.3, C. Striker 1.8.3, Classified Reclaimer 1.8.3, Classified Nomad 1.8.3, among others.
The best solo builds for me are the C. DF3 and C. Tactitican (or Hybrid Final Measure/Tactician Skill Build). You can breeze through almost anything with this one.
As a “rule” of sorts, if you are going to be killing with your guns, get 10,000 – 9000 Firearms, and focus in putting Enemy Armor % & Damage to Elites % on every gear piece that allows you to (it also depends of the geat set), and if you are going to be killing with skills, get 10,000 Electronics and put Skillpower % and Damage to Elites % in every gear piece that allows you to.
Other than this, check on YT for any 1.8.3 PvE builds. (1.8.3 is the last patch that was implemented in the game. If you don’t put it, sometimes you will get PvE builds that do not work nowadays)