hey Im pumped that you thinking of doing my sport, brother!
so look yeah Ive been doing this for about 7 years now so Im gonna give you some solid advice.
unless you just have loads of freetime to do multiple disciplines at once, start with bjj. bjj gets you really aware of your body, its orientation with the rest of space, and gives you an overall solid base, because most fights end up on the ground at some point.
roll with the guys in jiujitsu for a while, maybe til you get your blue, and then talk to your instructors, tell them you wanna mix it up, train thai boxing, filipino thing, whatever. filipino is really useful. my old gym did it too, and teaches you how to use a knife, which, if you plan on fighting in the real world, is an important skill to have.
you wanna do just ring stuff, I suggest bjj and muay thai. its a popular combination right now and for good reason. its the business. my last fight I won through the techniques I learned from thai boxing.
the most important thing you can do in mma is to not be a specialist. you wanna be well rounded. like wrestlers tend to drop their hands and so I kick them in the mouth. thai boxers seem to always wanna throw those cheap ****in leg kicks, so I hit them in the mouth or take them down, where they flop around like a fish, I get them in mount and pound on their face for a while.
Im not great at any discipline. The most important thing is to be aware of your body and read peoples timing, see what works for you, and evolve from there. By the time youve been fighting for a year or so (I got my bjj blue belt in 7 months, a little earlier than average), youll know your strengths and weaknesses.
the most important thing is to join a gym that has a good community. guys that come every day. guys that are down for the cause. check it out, talk to the instructors, try to see what the community is like. you gonna be doing this a lot so the people you train with is very important. my gym now, we got a solid core of about 10 guys that come every day. we hang together, go out to eat, party, chill, whatever. keep each other going. you skip, your buddy calls you like BRO WHERE YOU AT
you got any questions, send me a pm, Ill help you out. best of luck buddy