1) Join a corp.

2) JOIN A CORP.

3) Seriously. Join a corp. This game is not meant to be played solo. You can lone wolf it, eventually, after you learn the maps inside out and know where most of the engagements take place, and where you can find good cover, etc, but until then... join a corp. Lots of corps like taking noobs and helping them out, just look through the recruitment threads.

4) Become a logi, and learn what other people do by running around behind them, and paying attention to what they do. You can focus on learning instead of shooting, and still support your squad. Remember, you can create free PSN IDs, so create 2 or 3 more with 1 Dust character on each, and just let them accrue SP, until you figure out what you want to do with them. Turn one into a logi, and learn with him.

5) Don't worry about KDR, it means next to nothing in this game. The only thing that matters is the W. Some classes like logi frequently go negative -- yet they are orbital generators because of the WP they accrue. That guy on the winning side that went 3/10, and is at the top of the board with 2200 WP? Those are logis, and are critical to a team's success -- he's the reason you got pounded flat by orbitals 3 times during the match. Aim to be like him. Personally, when I play logi, I'm happy if I hit 1.00. That means that I was able to give as good as I got, which makes me the zero sum game -- I wasn't a slayer, but I didn't drag my team down either, and I still generated a buttload of WP during the match.

Another class that can go negative frequently is forge gunner -- I can easily go negative if I spend an entire Dom chasing tanks. If I go negative KDR, but we got the win because I was able to protect my squad by keeping 3 tanks at bay, but not actually kill any of them, does that make it a bad round for me? I think not.

In other words, KDR largely doesn't mean squat, unless you aim to be an assault slayer -- a "successful" match greatly depends on what class you are playing, and what role you were performing during the match.

Good luck merc!

Kind of an addition to this, if you're running w some people and get into a firefight, keep an eye on your surrounding and minimap to keep from getting flanked. Situational awareness is a very useful skill in this game.

Something else that might be a bit further down the queue of skills to get but at some point might want to think about putting some SP into it is "range amplification" (I think that's the name) gives a passive range boost to minimap/radar +10m/lvl if I recall correctly.
Dropsuit Upgrades>Core Upgrades>Electronics>Range Amplififcation
and no you don't need to equip booster mods to get the bonus

Catiously, the young Newberry pokes his barrel through the academy doors...

It's unfortunately only 10% per level, which for an assault suit means one meter.

I see, I take it I won't be getting very good K/D scores for awhile? Or is it still possible to get kills while supporting? Do kill assists help K/D?

What kind of skills should I be focusing on? Currently I put most of my sP into increasing my shields for all suites and some into weapon handling with assault rifles.