The fact that you stayed a fire main is a big part of your problem. The team you are running has little survivability. I was FM for a loooong time (like over a year) until the water meta finally wore me down and I switched to Earth. Let me tell you, ninja aren't everything, power is far more important. The hokage minato team I'm running right now beat someone with more power than I have AND they were running a Kurama Naruto meta. With enough power your team does not matter (granted the amount of power needed to overcome is variable)

As far as your group's GNW problem, the fact that the other group has rarer ninja can be compensated for. If you go back and watch Memo's GNW team building video it could help (it was around the time of Kage treasure release but it is still applicable). Instead of each person building their own team and then throwing 3 people together you need to group 3 people together and have them design ONE team. A team with synergy that make them stronger than the sum of their parts. I understand your woe's with GNW, trust me. But with this strategy we were able to beat our rival group which we had no business beating at this stage in the game.

Oh, and also as far as RNG events go this is my stance on that. I only take part in them if the redeemables are worth what I am spending (like getting charms packs, unbound runes, etc.) If the redeemables aren't really that worth it I might do one 10 spin, maybe two but I'm not going to spend thousands of coupons hoping to get something i probably won't get and then wish i saved those coupons the next week when a nice power items shows up that I need.

You will always be able to get those ninja slowly over time while compiling as much power as possible in the meantime. I am not a big spender at all but I have managed to reach 12th on S2. It just takes patience, perseverance, and a lot of discipline with your resources.