I would say that you should just learn one or two openings really well, and hopefully you know enough opening theory to survive any odd openings your opponent throws at you. If you like the King's Gambit, play it often and you'll have so much knowledge on it you'll be able to beat all who stand in your way! 
King's gambit
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I used the Kings Gambit for a while but then read from many masters that even if you play perfect it still has problems. Many of the greats prefer the Queens Gambit which I have been having a lot of fun with lately. Check it out on Wikipedia. It starts with D4, C4.
Have fun.
My favorite opening is usually a ruy lopez variant.
The King's Gambit is my favorite as well. While many will say that it leads to "inferior" positions for White, it's far from a forced loss by any means. Those who are inclined to follow only theoretically approved lines forget that our games are played against other people, not invincible chess gods. If you enjoy an opening, play it. Even if you lose you can't help but learn more about how you should play in the future. If you ever need any more support for the KG, hit up a Grandmaster games database and do a search for King's Gambit. You'll be surprised how many names pop up.
I am a great fan of this opening as well. Many people start learing it and are then steered-away from it by a fellow player due to its "inherent flaws." Because of its bad reputation, you can often surprise an opponent by playing it. I played it in a recent OTB tourney and completely stymied my opponent. He had no idea how to respond to its very potent threats, and made some grave oversights, leading to mate after only 14 moves. I couldn't agree with threat_of_mate more: "Even if you lose you can't help but learn more." Play what you love. Self-confidence can work wonders for your game.
from my otb experience, you should be able to play almost any opening that has a recognized name (ok, some people are going to post they know a name for 1.f3, but i don't-- lucky me) up till you face competition over 2400. then sometimes an opponent will prepare for you, and you will suffer for playing a second rate gambit. but till then, play whatever you find interesting. and hopefully by the time you reach 2400, you can find people to play fischer random with you, so you won't have to worry about theoretical refutations to your openings. i wonder at what level in online chess on chess.com you start getting punished for dubious openings, since your opponents might be looking in games explorer. 2200? 2300?
ps- i also like the king's gambit!! if only it were just a little bit better 
I play the KG too. I think it's theoretical status is reasonable, i.e. black can equalize fairly easily in a number of ways, but white is not in any trouble (theoretically; you can lose playing the KG, of course).
About whether you should play it, I really don't know. It's a rather complex opening leading to highly typical play, which has the advantage that once you familiarise yourself with it, you will have an advantage over a typical opponent of otherwise equal strength, but the disadvantage of not much of your knowledge "spilling over", like learning about a Caro-Kann position or an isolated queen pawn position helps your general understanding because they crop up so often. Also, the complexity might make it a bit out of the league of weaker players (like myself), although I think that should not be exeggerated. Unfortunately there aren't any good introductory guides to the KG that I am aware of, they would make the opening more accesible.
I like this opening very much . What is your favorite and why? Pls answer.Should i try some other openings also.