hey jk. ive been doing muay thai for 4years and some mma for about a year. let me start by saying its gonna be HARD work!
first you must also decide if you are going to compete in fights or are you only doing it for self defence and fitness. so it comes down to how competitive you want to be.
if you decide to take the mma seriously your going to have to focus on explosive and endurance training as well as a lot of high intensity cardio (believe me a 3min round is MUUUCH longer than you think

) and ill recommend 6days gym (shorter but more intense sessions) with 3days mma training.
if youre not going to compete stick to 4-5days gyming (start off with only3!) along with the mma. when you gym push yourself to take as heavy as possible and leave the cardio cos you are going to get hammered at mma training with that. also, on days you do both (gym+mma) try to space it out as far as possible or you are going to burn yourself out!
as far as supplementation goes, i used eca (before mma training) on and off and it definately helped me with the energy and intensity levels and also ethyl ester creatine before and after with my shakes. also you must up your calories cos you are going to need it. for the gyming part you can use the normal stuff you would if you were looking to bulk and gain muscle.
well thats just what im used to doing and it worked great so hoped it helped a little but im sure dj will know best as to the dieting and sups with such high level of training.
good luck!