Glad you have the common knowledge to realize the social circle is key to meeting women. Bars and online dating do not work generally.
Just to expand on what you said:
Meetup.com
Check out your local community college or County Park Systems for classes.
Just a word of advice, most classes at a community college (e.g basic Spanish) are through the adult education catalog (not full semester classes and last maybe 3 to 8 weeks (at most) with classes once a week
I took a basic drawing class through a county park system. Good class, but only met once a week for six sessions.
These environments are fun and conducive to learning, but you don't spend enough time with the people to really make a social connection.
Better idea: Take a full semester real class on a topic of interest.
Look into taking a class at night at a community college or university where you can audit the class (You do all the assignments and homework, but you don't get a grade) This will cost you $300 to $500 but you will be with college paying students. My basic French class was 3 months, two nights a week. I was 35 or 36 with a bunch of 19 to 22 year olds and there was one person older. I didn't make any new friends when I left, but it could work since you are with these people alot longer than a Continuing Ed. Class.
Another great one: Join a gym and take a intructor taught course (Hiit, Kickboxing, Yoga, Spin) Most of the participants are women.
Volunteer somewhere! (Park System, food bank)
Alumni events (alot of the same people go)
Good Luck!