Until you get decent, I would wash away all the scorestreaks first thing. You wont be going on any killing sprees just yet, those points are better spent on making you hard.

You can fool around at the firing range to find a gun you like, but I would personally recommend the AK, as it is full auto, very precise and it hits like a truck. The Red Dot Sight is very helpful, it clears your view of pesky iron sights and improves your accuracy. Silencer/Suppresor is very important, to fire on someone without giving away your position is important. Grenade Launcher is great for getting kills as a noobie, pair that with Danger Close perk for extra damage. Extended Mags, Stock, Foregrip and Quickdraw Grip are also great attachments, but I dont think their usefulness will truly help you until you become more skilled.

Until you learn the maps, carrying a Heavy Shield on your back is not a bad idea as you will likely be flanked around every corner. It will make ambushes a little more forgiving.

Exo-stim and Exo-Shield are good for absorbing a little more damage. I think it would be wise to use either of these until you get a feel for things. Avoid Exo-Overclock until you become familiar with the maps.

Running stealth perks is a pretty safe bet for new players, (Low Profile, Blind Eye/Cold Blooded, Blast Suppressor) will help you go unnoticed and give you a chance to get the drop on a few players. Toughness is equally important, but its only a clutch perk if you are losing gun battles by a hair, chances are you will die alot from players you dont even see, so its not as useful for those encounters.

Semtex is always a good choice for a grenade.

Since you're starting out, I'd recommend the FFA playlist, as you are more likely to be paired up against players of similar skill and you dont run the risk of getting pub stomped by parties and clans. If you play Domination, YOU NEED HARDWIRED.

Good Luck!