Oh God, I wish I knew what to tell you. But you know your family best and I think you're the only one who can truly know what to say and how to go about saying it. If I had to tell you something, I would say just get it over with and tell them. Say what feels comfortable, what comes naturally and, if they're worth anything, they'll still love and accept you.

If I were you, I would wait until I was ready. Tell the person you trust the most first. Someone you know wouldn't judge you for who you are.

After that, just keep escalating. Eventually, you will gain enough confidence to tell your parents. If they do not accept you, you need to be careful. For instance, don't bring home a significant other of your same gender if you know your parents won't react well. If they do accept it, then I'm happy for you.

As for the next part, telling your crush. This is an extremely hard thing to do. I, being a coward, would wait until I knew for sure how they will take it. As this is nearly impossible, just go with the flow. You don't want to startle her by saying it flat out. Just go slowly. I really hope that I helped you and I wish you luck.

Honestly, many of my friends are lgbt and I know how you feel (since I was feeling the same thing you are right now). I have a girlfriend and my whole school knows. That's how you start it. Let the whole school know by telling someone with a big mouth. You will get a lot of questions and it will be overwhelming at first but it'll blow over in a month or so. Trust me. The people who care about you (even your best friend/crush) won't care. They will love you anyway. Your best friend/crush might even come out to you after that (don't count on it. I was the exception). After a while people in your neighborhood will talk about it and one of your parents will overhear. They will confront you and you just need to be honest with them after that. Trust me it works. If you can't bring yourself to do it now, just wait till your ready.

dont worry i know how you feel. i am afraid to tell some of my friends and the people i live with. b/c my family is christian toooo but let them know that you want them to accept you for who u are and let them know that you are who u are and there is nothing that can possibly change that. with your crush if she is also bi then you wouldnt really have much of a problem but if shes not just let her know how you feel but also let her know that u respect her enough that you will not force her to do anything.

There really is no easy or gentle way of coming out.
All I can say is the earlier you tell your dad the better
They might accept it and then again they might not.
But you owe it to yurself to come out