back to topic it all depends on ur ear, some people just have a knack for developing dope melodies in their head,
some people have a knack for manuplaint samples and some peopel can do both.
as far as music theory is concerned their are 2 sides of it, their is the basic shit like counting bars, knowing triads etc... and then their is the advances shit.... for hip hop unless ur doing some sort of orchastion u dont need it
I say this again and again on here ALL music theory does is explain what most talented people do naturally. U CAN HAVE A MASTERS DEGREE IN MUSICTHOERY, i does not mean u will compose dope shit , all it means it that u understand the structure of music, i really want u guys to understand this...
I went to school with some of guys who knew all the theory in the world and couldent compose a melody to save their life.... Music theory is the structure of music and wasent developed fully untill the early to mid 1800's, bach dident know music theory as we know it but look at the music he composed, point is , it comes down to your indivdual talent
As far as sampling and composing, well i do both, and i can tell u each invloves its own unique skillset... dont limit urself to one or the other or try to learn one at a time, mix and match
alot of times, i will alternate, make sampled beats one week and composed beats the next, since they involve difffernt skills it keeps me fresh
Also learning how to play the piano wont nesscarly make u a better producer, their is difference between learing how to play others peoples music and developing ur own.... so dont think taking piano lessions is automatically gonna make u dope, that aint the case at all, trust me..
my 2 cents