Girl issues (i'm a guy, not a typical guy)

I'm a junior in high school. Last spring (2013) I broke up with my girlfriend after dating for 7 months. Neither of us did anything wrong, I just realized I lost interest in her and I needed to end things before they got more serious. Over the summer, a credible source told me that one of my ex's friends thought I was "really cute" ( girls love to use the "c" word). I was kind of attracted to her when I was going out with my girlfriend. I realized I wanted a girl more like her which contributed to my decision to break up. After not talking to my her in about 6 months since we broke up, my ex and I have been texting. I made it clear to her that we are never going out together again, which I believe she accepted, and now we are friends. So now I am doing a sport where I see my ex and her friend who thought I was cute. I go to a different school from the two girls, so the only time I really see them is during sports. I am still interested in the girl who thought I was cute, but I'm afraid this is either not ethical, or possible because the girl wouldn't want to go out with her friend's ex(me). I'm an outgoing and social person when I want to be, and I can flirt with girls, but I'm naturally a very shy person who doesn't like to make the first move (too bad I'm a guy). I have no idea if the girl I like even likes me. I notice that she likes all of my photos on Instagram, but does that mean anything?(probably not but I wish) also, today at practice we walked by each other. She was with another girl (for girls are ALWAYS found in pairs). I waved at her to say hi. I definitely know she knew it was me, and I would expect her to at least say a hello, because this girl is the most social, outgoing and ADHD ridden girl I know! But she kind of looked down or past me and never saw my wave to her. I just wanted advice on: is trying to go out with her ethical( I'm a very sensitive person, I used to cry as a child for my stuffed animals that I didn't snuggle with one night that had to spend the night at the end of my bed, because I had a lot of stuffed animals!) second, if I decide it's okay to go for it, how would I go about doing so? We go to different schools and do different events, so we aren't forced to spend time together easily. Part of me wants to hang out with my ex so I can be around her friend but I feel like that's a jerk thing to do. I forgot to add that I really want a girlfriend because I want a partner to share feelings with, have fun with, and get to know well. I'm not a typical teenage boy who only wants a girl for sex. I would love any advice, because being a teenager can be very confusing at times.