Honestly a lot of it comes down to play style... I'll break it up into sections.
Perks. Blast Suppressor is a must so that you don't show up on the mini-map every time you boost. People also tend to spam UAVs a lot so Low Profile (Perk 1) is on almost all of my classes to counter this. Note also that if you do any Ranked Play, UAVs are banned so this becomes unneeded for that. Beyond this I tend to pick perks as counters to what the opponents are doing. Other team lobbing grenades? Put on Flak Jacket. Lots of aerial scorestreaks (Assault Drone, Warbird, etc)? Blind Eye. Hard Wired is invaluable as a counter to stuns, EMPs, and System Hacks (which are used a ton especially in Domination). Toughness is also very underrated if you're in a lot of face-to-face gunfights.
Guns. Right now the best all-around guns (at least on console) are the ASM1 (SMG), Bal-27 (AR), Ameli (LMG), and MORS (Sniper). Weapon balancing is coming along well so more guns are becoming viable, but most of the secondaries aren't worth a Pick-13 slot IMHO. Check out Drift0R's YouTube channel (also on here: /u/Drift0r) - he does really good gun guides that should help narrow things down for you.
Streaks. I rarely if ever run anything besides a UAV with the support module, since each streak costs a Pick-13 point. Assault Drone can be dirty with rockets and AI, as can a Warbird with AI. However a lot of people run Blind Eye (counters AI scorestreaks) so sometimes that wouldn't work out too well. A Sentry Gun can be great for holding down objectives too. The streaks aren't bad, it's just that I feel like they're too expensive for what you get a lot of the time.
I personally tend to play pretty aggressively around objectives, so my classes come from these combinations:
Gun option 1: ASM1, Quickdraw, Foregrip, Advanced Rifling
Gun option 2: Bal-27, Stock, Foregrip, Quickdraw
Perk set 1: Low Profile, Fast Hands, Blast Suppressor, Toughness
Perk set 2: Low Profile, Blind Eye, Toughness, Hard Wired (to counter aerial streaks and system hacks)
Exo/grenades: I always run Overclock, and then either a Trophy (with the Tactician wildcard), double Semtex, or double Stun. If you play Search and Destroy (or Search and Rescue) then Exo Mute and Frag grenades are fantastic.
Obviously your load outs might look a lot different than mine depending on how you play - hope this helps!