Bobby Fischer used to play with the white pieces against the Najdorf Sicilian (1.e4 c5 2.Nf3 d6 3.d4 cxd4 4.Nxd4 Nf6 5.Nc3 a6) - and win. Then he would take the black pieces in another game - and win with them. Some players - and some openings - are like that.
The Jerome Gambit is not. If you have the white pieces and play the Jerome against a knowledgeable and booked-up opponent, chances are that you are going to have a rough time of it – unless you're playing a "weaky" (Bobby's term) that you've given Jerome Gambit odds to. *
Playing 1.e4 e5 2.Nf3 Nc6 3.Bc4 Bc5 4.Bxf7+, you are counting on the element of surprise, shock, and awe to level the playing field. Therefore, you need to be aware of every trick, trap, and pitfall (or "caltrop" as Tim McGrew used to say) available to you so that you take advantage of every chance that comes your way.
Hence this series, "The Jerome Gambit For Dummies". (No jokes, please. We know, we know...)
* Some thoughts on the art of odds-giving, from the age of the Jerome Gambit:
Chess At Odds of Pawn and Move compiled by Baxter-Ray (1891)
Considering the large number of works published for the purpose of teaching a knowledge of the game of Chess, it must appear strange to the ordinary student to find so little information available in regard to Openings at Odds. Odds-giving has never received the attention it deserves from the analysts of the game. Yet it is very popular, and is rapidly growing in practice ; indeed, it is absolutely necessary for every Club, and a very large number of private players, to regularly introduce odds into their games, with, at present, little or nothing to guide them as to the best means of commencing play.
A Popular Introduction to the Study and Practice of Chess. Forming A Compendium of the Science of the Game by Samuel Boden (1851)
One may often hear persons declare that they think it cowardly to take odds, that they had rather be beaten on even terms ; or that the removing of a piece, in odds, must spoil the game. All this is sheer nonsense, and only bespeaks utter ignorance of Chess. A game played even, where one party should be rendering the odds of a piece in order to give the other a chance, will have no interest for the one, and little pleasure for the other. If the weaker player has no chance, of course the stronger player can have no sport.
The Australian Chess Annual Edited by H. B. Bignold (1896)
If the handicap given is a fair measure of the difference in skill of the respective players, the odds giver can only hope to neutralise his deficiency in material by superiority of development. Assuming he has the move, it immediately becomes a matter of the utmost importance to adopt a suitable opening. But what is a suitable opening ? The answer to this will vary with circumstances, and on the player's ability to gauge them will to a great extent depend his success as an odds-giver. It is very certain that every player has some particular style of opening, which is in consonance with his turn of thought, and in which he will appear to the best advantage. If you can form some idea of your adversary's penchant, and avoiding it, lead him on to less familiar ways, your chances are, perforce, improved. Assuming you are the better player, if it should seem to you that you have both the same cast of mind, it is a matter of very nice consideration whether it will pay you better to meet him on his own ground, which is also yours, or lead him on to ways strange to both of you, trusting to your greater skill to gain an advantage on the spur of the moment. In choosing a gambit it should be borne in mind that if the one adopted is familiar to the adversary, the game is almost hopelessly compromised, since the initial difference force is already increased without any positional recompense. The writer has a lively recollection of giving a 5th class player a Rook and Knight, himself being in the 1st class, and receiving 14 moves of book defence to the Allgaier he ventured on ! In this dilemma, though it may appear fanciful, perhaps your adversary may himself give you the least hint. If he is a careful, cautious man, square-jawed, deliberate of manner, apt to weigh his words — perhaps even attach too much weight to them — given to loading his pipe with the utmost deliberation, and lighting it as if it were a solemn function, is it too much to premise that he belongs to the class that loves to castle early and oppose a solid phalanx to the advancing foe ? Perchance an Allgaier, or a Kieseritzky, whereby his cherished scheme of castling is rendered impracticable, may utterly rout him ! If he is of the opposite temperament — nervous, painfully excitable, given to squirming with impatience should you appear unduly slow to move — a Giuoco, with its orderly development, may entice him from his entrenchments to be more easily dispatched. In general, of course, he will belong to neither extreme, and classifying him will be a work of some difficulty, but to one who cares to succeed, a knowledge of his rivals can never be without advantage, in chess or the sterner warfare that it dimly shadows forth.
4.Bxf7+ Kxf7 5.Nxe5+ 
5...Ke7 
Things have settled down, and White is ahead two pawns. It's not a very complicated position.
