I do not know how old you are. I did not meet my husband until I was 34-5. I applaud your volunteer work. I would work harder on getting a job so you will have more money or on volunteering and being in clubs or school, being out where there are people. I would work first on finding another good guy friend so maybe you can become part of a group of guys and that might naturally bring you into contact with more girls, rather than trying to get friends of my sister to notice me. If you remember the names of some of the others in the group you use to hang with, call them up out of the blue and say "hi" and see if you can get together since your one contact (Rosa?) did not work for that.

As I am sure you know, people who are part of a couple or group have a much more complicated social life and it can be very hard for people to break in from the "outside" because the dynamics are so complicated. There is a lot of spontaneous getting together at the last minute and unless you are "there" then, no one is thinking of those they can't "see". It would not occur to me to say, "Oh, wait, let me call Djinn8. . ." not because I wouldn't want you along but because where we are going, how we're getting there, when it start, who's going with whom and all the actions are so immediate and getting a "group" to wait, doesn't usually happen. Getting the "ball rolling" all in one direction, if you suddenly/late throw another person in there, that is like a bump in the road. The energy to do something "new" takes up all the room and there is no room for "extra" in that case.

As far as meeting single women, I would hang out where single women might hang out, in a cooking or other class (music, travel, books/reading), where there are schools/teachers/children, etc.

Become part of a group as part of the group. Volunteering usually makes you part of a volunteer's group so pay attention to that group rather than the group you are volunteering for? You were hosting a D&D, that makes you the host rather than one of the many others; be part of a many other (like in your walking but there are perhaps not enough people there or any continuation possible (you walk and then you're done; people may or may not show up for another walk)). I am a girl and met a good girlfriend as part of a library group, working over time on the book sales they had. We "shared" an older women whom we thought of as a mentor of sorts. The three of us often went out together and the older woman had me over for a holiday dinner when I was not invited anywhere else. The girlfriend and I did Irish pub crawling together and went to a concert to see Makem & Clancy, etc. I helped her move. Get a few guy friends to hang with and play football with every 2nd Saturday or something? You'll all go to a pub afterwards for a pint and then you can hit on their sisters and their sister's friends