If your going for the current synthy wiz kalifia type or dj toomp/ TI sound you can't go wrong with F#m, Am, and Gmaj
Some chord progressions that usually work for me for those kinda beats are 1,4 (simple but jammin all the same, 6545, and 1415.... Throw in a lil one finger 3 note melody, a lil bell or mallet instrument harmony and a rolling dirty synth lead and u got the current type of hip hop sound that these young rappers like to flow on.
Im no expert by any means but that lil simple formula seems to work, for whats out now atleast...and of course theres a million other ways that are just as good to go about it!
Play with arpeggiators and gates too!