if u want to gain muscle without gaining fat just follow a maintenance diet, roughly 15 X bw for total cals consumed each day with whatever macronutreint breakdown u choose, around 40/40/20 carbs/pro/fat i prefer. though you will gain muscle at a much faster rate when bulking. i prefer to do a cutting then maintenance for a while, thenb ulk during winter and fall and cutt towards spring, maintenance during summer. though i had some problems with bulking and cutting recently, hopefully thta doesnt happen next time around (ended up gaining 26 lbs and only kept 4 lbs at about 1 or 2% lower bf than when i started after i finished cutting)