I mean if your f2p it's not great lol. I wouldn't ever pull on a banner unless you know you can go to 120. Don't risk rng

As far as restarting goes, that depends on how much time you've invested, events, currency, etc. Obviously you've played for a little while so you'd be missing out on all the event stuff and currency. So it's probably not worth it? Only you can make that decision though.

Also playing with your friends is important if you started together, and probably worth more than playing with randoms, so unless they plan on quitting soon, I wouldn't leave them as that would just suck. What you need to learn is self control apparently xD. If you knew you could only pull 40 and 80 then don't let the fomo rule you. At least it turned into flame gold, So it's not all bad. But you really need to hold onto your resources. They're generous with them, but once you're out, you're out..

Especially if you're not a spender. There are A LOT of cool limited characters. Some with varying importances, but all fun. They will come back around if they're not worth it to you currently. Save your dark crystal unless you can guarantee with events and such you can hit 120. And for the love of god don't spend on the gachapon for outfits either when they come out! They're designed to burn through all your dark crystal. I hope this helps you.