I am making game music by myself, and, basically, all you need is:
Knowledge in music, good musical ear is a plus. - You get this the easiest way by going several years at musical schools playing any instrument (I play the saxofone, mainly the alto saxofone, for example).
Knowledge in the program - For this, I strongly recommend you to start with looking on Youtube tutorials, and when you are at the point, that you know what is going on when you open and use the different things like Piano Roll, Step Sequancer, Playlist, Mixer, Browser, I strongly recommend you to look at the works that they are showing in Youtube. Once you think you know how to make music like the professionals, just keep practising in fl, as much as you can, because that way you get experience and you know what to do. Once you have finnished one song, upload it here and other places you know, for C&C, where it is many musicians hanging around that might help you getting even better.
Good and wide creativity - I have no clue if there is any chance to improve this by training. People are usually just born with or without this.
Knowledge in how to build up melodies - This part is only improved by listening to the music you want to make a lot, watchning other melodies (One way is for example to import any midifile, and look how they did this, and try to make something similiar.), and practising on making the same kind of music a lot.