Akido is, in my opinon, the only martial art that anyone should learn. There are at heart three kinds of martial arts - weapons, striking (kicks/punches), and wrestling. Aikido is a mix of wrestling and weapons - in large part because striking doesn't work very well against someone using either weapons or wrestling. Aikido concentrates on defense and relies heavily on body mechanics. For example they teach you to hold your opponents hands in a way that is easy for you to do - using major muscles - but is hard for them to escape - because their muscles have no leverage. One of the more important things they teach is how to fall safely. Aikido is less than 100 years old and related to jujitsu. At the dojo I took lessons in, weapons training was secondary to learning their grappling techniques.
It is relatively cheap compared to most martial arts. They usually offer free or cheap intro classes, then require you to join the dojo and pay a monthly fee. This helps ensure you to come often enough to actually learn.
It's is not extremely hard to do, but it does take a lot of practice to do it well. Similarly, it does not require a lot of strength, but it does involve significant physical contact.
It is usually more male than female but does have women partaking. As it doesn't require significant upper body strength, women are just as capable of becoming fantastic in it as men - don't be surprised if your teacher is female and throws you around like a rag doll. Unlike most martial arts, it has significant older population. They do accept teenagers, but tend not to have young children. Because it avoids striking, it's not as violent as other martial arts.
I took classes here: