What do I (15M) do when two girls (15F, 14F) both like me?

For context, I’m 15 and in Year 10, so I’m pretty stupid. But, I like to face things with logic and tend to stress over the future, so I’m trying to address this issue now. When I was in Year 7, I met this girl - who we’ll call Ruby - and she became my best friend. I liked her, and she liked me, and though I knew I wasn’t ready at the ripe age of 12, I got into a relationship with her. I won’t lie, everything was amazing. She was just like me - kinda awkward, Filipino, shared my interests, humour, extracurriculars (student council, debate team, school play) etc. However, things started to change (as they tend to do when you’re a teenager) and my perspective on life shifted. Around Year 8 I developed depression and it was difficult for me to maintain my current relationships, so we broke up. However, I started seeing a psychologist since then and things began to look up. Eventually, I got back into a relationship with Ruby, and we still both liked each other a lot. But after everything, I felt I was beginning to mature, and I wasn’t the same obnoxious little kid I was at the start of the relationship. Ruby could tell too, judging by my different attitudes and treatment (like avoiding things that now made me uncomfortable like PDA). I felt myself growing as a person, finally making new friends and exploring who I was following that depressive state, but Ruby didn’t like how I was changing. Because of that, we became an on and off relationship, as I knew we couldn’t treat each other right, and that I was a different person than I was originally. But as a stupid selfish teenager, I still made stupid mistakes. I’m not gonna lie and say I didn’t lead Ruby on. Every so often I would message her if I felt lonely, but I would regret it immediately after. My lack of self control made me feel immensely guilty and I just feel so bad for taking advantage of her. Ruby has never stopped liking me, probably because we never really stopped talking to each other. But here’s where things start to change. Just recently, my school had a band competition for nationals, and there, I spent a lot of time with my friend who we’ll call Sapphire. She’s the year level below me, but I’d been friends with her since Year 8 (through the school play). She also dated my best friend in the past. The week of the tour, Sapphire and I spent a lot of time together, and I told her I liked her just to get it off my chest. I didn’t expect to have feelings for her, and I honestly didn’t want to considering circumstances, but I couldn’t help it and just wanted to get it out of the way. However, she ended up reciprocating those feelings and asked to get together. I figured it would be fine if we just took it slow and kept a private relationship. However, we’ve been together the past week and been out twice, with the relationship essentially becoming public. I really like her, and I admire her intelligence and articulation most of all, and though it hasn’t been long, we’re comfortable enough to be vulnerable with each other now. My best friend found out, but he said he can support us being together. We’re the same age, so I feel we’re both mature now unlike my previous relationship. The only thing holding me back from just being with her is Ruby. I can’t just forget our history, especially the course of over three years together, and I can’t just forget all of our good times. When I told Ruby that I had moved on and sincerely apologised for leading her on, she called me out for being unfair. I know she was right. Ruby and I hadn’t been in an actual relationship in a while, but it just felt wrong to just abruptly tell her I couldn’t do this anymore and cut contact with her (even if I think it was the mature thing to do). I still think of Ruby (which of course I will, she was such a big part of my life), especially when people ask about her upon finding out I’m with Sapphire. Here’s my split: Ruby shares my history, time, and culture. Sapphire is exploration, maturity, and uncertainty. I’ve just started dating Sapphire, which I admit might’ve been an irrational decision, so I’m not sure how much I can do now. She is of a different year level, ethnic background, past, etc. so everything is new. Ruby, in contrast, seems to be a “safer” option, but is it more responsible? Idk guys I’m torn. Thanks for everything if you’ve read this far.