EDITED:  2. ...Bc5 (sorry for the typo)

thanks. I've been having trouble with this opening for a while

Why don't you just say "How should I handle the King's Gambit?" Opinions vary on this question. If you take the pawn, you can expect 3.Nf3,  when I recommend 3...d5, with a practically won game for black. If you're the conventional cornball type, and you want to hang on to your goody (the f4 pawn), you can play 3...g5, then after 4.h4? g4!? You can then expect white to try and worm his way out of the mess he's in with a lot of crazy gyrations, such as.....

Korchnoi and Zak demonstrated decades ago that 3...d5 leads to a better endgame for White.  Holding on to the pawn with g5 is good if you are extremely booked up and good on defense.  Declining with ...Bc5 is simple and good.

2...d5 falkbeer counter gambit

You can try the Cunningham: 2. ...exf4 3. Nf3 Be7 (but don't play Bh4 except for rare occasions). But they can always play 3. Bc4 and throw you a curveball.

2...d5 3.exd5 e4! Falkbeer Counter Gambit

OK. I admit it. 2...Bc5 is pretty good for black. Most players choose the done-to-death 2...exf4. Incredibly, after 2...Bc5, the rather passive looking 3.c3 may be best for white. White has a bazaar alternative with 3.Qh5!? Check this out...

I recommend giving up e5 and switching to 1...c5

The "best way" depends a lot on your style and preferences. If you're greedy take the pawn and try hanging on to it at all costs, there are several ways of doing so. If you don't like accepting gambits play...Bc5. If you like counter-gambits play 2...d5 (Falkbeer Counter-Gambit). GM Evans used to say The best way to refute a gambit is to accept it but that may or may not work for you. I rarely accept genuine gambits but I always accept the KG because I've had good luck using Fischer's Defense (3...d6) but again, there are many other defenses available to Black in the KGA.  Whatever you do I suggest you start using the same defense all the time until you have some basis for either abandoning or keeping it in your opening repetoire (ie several results at least). And play through as many GM games as you can using whatever line you decide on playing. You can also look up articles and annotated games with your pet line here and by using a search engine. GOOD LUCK!

In the 1st line mentioned by Melvin Bluestone above instead of 5. Ne5, interesting is Ng5, and if 5...h6 then 6.Nxf7 Kxf7 Qxg4 gives a strong attack for the knight sac, white can continue with moves like Bc4, d4, Bxf4, O-O, Nc3-Nd5 etc (depending on blacks responses) to intensify the pressure.  I have had this a few times in bullet/blitz as white and mashed my opponents easily. 

If 3.Nf3 d5 was a 'practically won game for black' grandmasters would have given up playing it 100 years ago.  Per the Chess.com Game Explorer this move order gives white winning 40.5%, draw 24.8% Black winning 34.7%!

 Of course, I was kidding with that "practically won game" stuff. I believe 3...d5 is the Abbazia Defense, which also has the paradoxical name "classical/modern defense". It leads to pretty lively play after 4.exd5 Nf6. Also playable, but less well-known are 4...Bd6 and even 4...Ne7!? If you're a real nut, you can try 4...Qxd5 5.Nc3 Qa5!? ........ icecoldalex is right: In the other line, 5.Ng5 is a good alternative to Ne5. You wanted advice for black, so if you come up against this, don't try 5...h6 as the sac on f7 is practically forced and no fun to defend. Best is supposed to be 5...Nf6, but even then I guess white could try 6.Nxf7!?

lol...yeah gosh, there have to be some books written on this thing...

I think you ought to have the Kings Gambit Declined in your repetorie.  If you find yourself facing the gambit often, you can also spend the time to learn one of the Kings gambit accepted lines (or a counter gambit), but staying fresh on these lines is hardly worth the effort if you just see it once in a while.

 Wait a minute! Wait just a gol-darned minute! Wasn't it Teddy Roosevelt who said "The way to refute a gambit is to accept it!" Whaddya' tellin' the guy to decline it for? That's no fun! .......... Seriously, though, of course you can decline the King's Gambit. The most adventurous way is probably with the Falkbeer Countergambit, 2...d5. This line has a lot of good points, not the least of which is a cool name, Falkbeer! If you want to out-and-out just not take the freebie pawn, I recommend the crazy Keene's Defense: 1.e4 e5 2.f4 Qh4+!? 3.g3 Qe7.

2...Bc5 is probably best in that you get positions where you can actually have an idea of what's going on. I just take and play 3.Nf3 h6. For some reason White rarely ever manages to grab the pawn back. It's been practically a forced win for me lol.

Bc5 would be best

3...d5 is not practically won for black, what kind of nonsense is that.  There is still a whole game to play. 

Oh, that's not complicated at all!!