Need help on improving.

Starting rating does not mather. You can start with 2200 if you like, it will be sorted up after 5-6 games.

For pawn structure and piece development, If you hold center and hold it strong, you can attack right, left of mid. If you push only your K-side, or Q-side pawns, there is not much options for you. Even moves like c4, f4, c5 are made so you can put more pressure on center.

Simple as that.

This could help too

Chess Principles

01.  Develop your pieces quickly.
02.  Control the center.
03.  Try to put your pieces on squares that give them maximum space.
04.  Try to develop your knights towards the center.
05.  A knight on the rim is dim.
06.  Don't take unnecessary chances.
07.  Play aggressive.
08.  Calculate forced moves first.
09.  Always ask yourself, "Can he put me in check or win a piece?"
10.  Have a plan.  Every move should have a purpose.
11.  Assume your opponent's move is his best move.
12.  Ask yourself, "why did he move there?" after each opponent move.
13.  Play for the initiative and contolling the board.
14.  If you must lose a piece, get something for it if you can.
15.  When behind, exchange pawns.  When ahead, exchange pieces.
16.  If you are losing, don't give up fighting.  Look for counterplay.
17.  Don't play unsound moves unless you are losing badly.
18.  Don't sacrifice a piece without good reason.
19.  If you are in doubt of an opponent's sacrifice, accept it.
20.  Attack with more that just one or two pieces.
21.  Do not make careless pawn moves.  They cannot move back.
22.  Do not block in your bishops.
23.  Bishops of opposite colors have the greatest chance of drawing.
24.  Try not to move the same piece twice or more times in a row.
25.  Exchange pieces if it helps your development.
26.  Don't bring your queen out early.
27.  Castle soon to protect your king and develop your rook.
28.  Develop rooks to open files.
29.  Put rooks behind passed pawns.
30.  Study rook endgames.  They are the most common and most complicated.
31.  Don't let your king get caught in the center.
32.  Don't castle if it brings your king into greater danger from attack.
33.  After castling, keep a good pawn formation around your king.
34.  If you only have one bishop, put your pawns on its opposite color.
35.  Trade pawns pieces when ahead in material or when under attack.
36.  If cramped, free your game by exchanging material.
37.  If your opponent is cramped, don't let him get any freeing exchanges.
38.  Study openings you are comfortable with.
39.  Play over entire games, not just the opening.
40.  Blitz chess is helpful in recognizing chess patterns.  Play often.
41.  Study annotated games and try to guess each move.
42.  Stick with just a few openings with White, and a few openings with Black.
43.  Record your games and go over them, especially the games you lost.
44.  Show your games to higher rated opponents and get feedback from them.
45.  Use chess computers and databases to help you study and play more.
46.  Everyone blunders.  The champions just blunder less often.
47.  When it is not your move, look for tactics and combinations.
48.  Try to double rooks or double rook and queen on open files.
49.  Always ask yourself, "Does my next move overlook something simple?"
50.  Don't make your own plans without the exclusion of the opponent's threats.
51.  Watch out for captures by retreat of an opponent's piece.
52.  Do not focus on one sector of the board.  View thw whole board.
53.  Write down your move first before making that move if it helps.
54.  Try to solve chess puzzles with diagrams from books and magazines.
55.  It is less likely that an opponent is prepared for off-beat openings.
56.  Recognize transposition of moves from main-line play.
57.  Watch your time and avoid time trouble. 
58.  Bishops are worth more than knights except when they are pinned in.
59.  A knight works better with a bishop than another knight.
60.  It is usually a good idea to trade down into a pawn up endgame.
61.  Have confidence in your game.
62.  Play in as many rated events as you can.
63.  Try not to look at your opponent's rating until after the game.
64.  Always play for a win.

I'm not sure if you guys have looked through the game I just played. I think I threw the other guy off by being stupidly agressive.

Coreect me if i'm wrong, but instead of cxb4, would moving something else have been a better move? I think at that point, he could have either seen it comming and moved his rook away or leave it there (in which case I would have moved bxc3). 

Like chessplayer4402 said, it was easily avoidable and there was a bunch of things that could have gone wrong.

Normally as white, I would have gone for the center (Nf3 would have probably been my prefered move), but I really had no what idea what to do as black...

It's this thing that I came up with which rarely ever works. The whole idea of moving that b pawn was to get his c pawn out of the way so my bishop could take his castle out (see move 13 and 14). Thats the stupid castle thing :S