I haven't started a true transition yet, and I still wear dresses to church because its kind of expected and I grew up with these people and it might be a hard thing for them to accept so I'll probably have to move before I can. So I don't think dressing up in girly clothes from time to time is really abnormal, even if you're a cheerleader, though I admit it is rather uncomfortable for me, personally, to wear the girl stuff. My mom got me a kind of male blouse and I feel more comfortable wearing that, even if I have to wear the skirt.
In high school, I had almost no friends at first during my first year due to everyone just changing. Then the next year I made new friends and decided to start fresh and I did find better friends and everything was good for me. I took a risk with one of my new found friends by telling her I was FTM transgendered because I trusted her to be level headed and I guess I was good with my judgement. I, myself, realized I was transgendered the summer prior so none of my previous friends knew and with their reactions to transexuals in general was negative. Anyway, she helped me to tell my other new friends, who happened to be her friends too and they accepted me for who I am and didn't judge. And we kept it to ourselves and didn't tell anyone else in the school, but I had some people to confide in.
I guess the thing that I learnt was, if they're your friends and they really care for your well being and want you to be happy, its easier to tell them. If you're unsure what their stance is on people who are transgendered and whatnot, why not bring the topic up? You don't have to say you think you might just be FTM, but try to find a topic that would bring up the subject. If their reaction is good, then perhaps they will accept you with open arms with who you have come to identify as. If they can't, then perhaps you need to find some friends that will.
As for your parents, I truly don't know what will happen, but I can understand your concern. My parents, for example, are very religious people and I am as well. However, my parents are very understanding and compassionate people and they raised me in a way to show kindness and love toward others. I actually remember coming out to my mom, when I was 15, out in the backyard and we were sitting at the table. A few months ago I finally found out what being transgendered meant and that it was the definition I was looking for, and I was tired of keeping it in... so I told my mother, right to her face my problem and that I was transgendered. And she just sat there and listened to me, and she was very understanding and not as judgemental. It still took them a while to get certain things, and even now they're still learning, but they took it well. I guess where I grew up and how I grew up, I wasn't particularly afraid of coming out or caring what people thought. I did want to keep it a private matter from some kids at school though, but even then, I don't think I would have minded. We had a student who was openly gay and no one cared. However, not everyone is as fortunate as I am in those regards.
Your experiences could very well be different from mine. You really wont know the true outcomes unless it is said. And that decision is up to you when you feel the time is right. Not everyone was as or is 'bold' as I was to say it directly to my parent's face. Some did it through phone calls, notes, letters... some even waited a long time before they went ahead with it all. And theres no shame in any of those either.
Just remember, as far as your personality and interests go, theres no set in stone way of being FTM. Its the same way as any guy liking something that may be considered 'girly' or 'unmanly', we're individuals and our personal interests, personality traits and preferences can be just as unique. You don't have to be a macho man. I don't believe in a 'proper recipe' for someone who is FTM. We are all different, just everyone else. There are common traits and similarities that occur in the FTM community, however its just the same as being a born male or born female. Theres room to be different, no one will think you less if you are.
An example would be that I like a lot of 'manly' things and I like to strut around and all that jazz. However I have some personal interests that might be considered 'feminine' and I worry sometimes if that makes me less of a man, but then I think... No, there are biologically born males who do share the same interests as I do. I'm no different than them.
I hope this helps you at least a little. I don't mind contacting you one on one either.