Hello Kira, I would suggest checking out all the dojo/gyms in your city, and when you see what might suit you then join. Some dojos (like mine) allow you to do some trainings without paying so you can see if this is what you like. So good luck and take care
Just my opinion of course, but stay away from anywhere that won't let you participate in a normal class prior to joining.
Recently I ran into a school that wanted me to pay to try them out. $60 for a uniform and two lessons. They "gave" me a "free private" lesson, but that doesn't give a feel for what the classes are like. In the end, the instructor/owner was pushy and told me outright I was wasting his time when I said I wanted to look around. And they had the nerve to call me last night with their latest "special."
There are a thousand different opinions, but modern thinking is you start from the ground up. Which means see if there is a nice Judo or BJJ school in your area. Preferably one with a kids program that promotes competing in tournaments.
Not that you have to compete, it just shows that the school is a part of the larger Martial Arts community.
Of course there are many other great arts to chose from as well, but you will never be sorry for learning a good base like Judo or BJJ.
Good Luck.
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Undefeated in all of Asia!