Here's the deal:
There is no "best martial art" (MA).
The human body is a finite thing - there are only so many ways it can move, there are hard points and weak points. Most MA use the same principals - they typically just emphasize one aspect over another. "It's all good"
There is room for disagreement, addtiions, subtractions, etc but basically you want to cover/learn/do:
o Aerobic - sprints or aerobics, etc
o Anerobic - "endurance"
o Strength -
o Body toughening (falls, hitting, etc)
o Techniques against common attacks
Punches (hand strikes)
Weapons (anything that lengthens or strengthens your sphere of offense/defense)
When starting from ground zero (no MA training) taking ANY martial art will be beneficial. As I said - the principals are there in all of them.
Earning a black belt (okay, "getting very good at") ANY MA will set you up for success in others - as long as you don't fall into the trap of "my system is best". No, it's not.
So, pick a school near you (convenience). Most will let you take a free lesson and/or observe some classes before you sign up. Avoid signing a "One Year Contract" which seems to be the rage right now in the biz. Also, it's like college - for every hour of class, you need to put in several hours of practice. You need to practice every day.
I recommend a school because most people can find one, but over the years, the best instruction I recieved was from private instructors. Instructors who did not charge or who charged only a very nominal fee. They taught for the love of the art or to "create training partners" and so on. These types are hard to find but if you can find one - do your best to "sign on" and then train hard.
I have passed on this concept over the years by taking on students and training them for free. I will tell you from an instructor's perspective it is a joy to teach students who are "into it" but gets very frustrating teaching those who obviously don't put much into this free, quality training.
Also, the more real sparring you do, the better you'll be. Many schools don't spar at all (bad) or spar only for points (no real hits - also not good). Many won't let beginners spar but this is actually a good thing - better to learn the basics first or you will just revert to "caveman fighting" under stress.
Hitting and getting hit, grabbing and getting grabbed, throwing and getting tossed - all have a way of "focusing the mind".
So - get fit.
Learn and practice the basics.