As a gamer, I have given a question like this a good bit of thought. Actually, I just game out to my closer online friends today. In fact, only my wife, 1 local friend, and 2 online friends knew before this. Basically, I spent a LOT of time thinking on it.... I'm pretty popular on Facebook (almost 900 friends). Almost half of them actually interact with my posts somehow, out of the ~600 active accounts.
I thought long and hard on how to approach it, because I have the added misfortune of living in the bible belt, rurally near the gulf. As such, I don't want to "come out" in public locally, until I'm actually male failing, so I didn't want some people TO know... which made my situation harder.
For the friends I had on my page, I gauged who I wanted to know about "the new me", with my transition. Since I didn't want to upset anyone, I gave people a chance to comment on my post or HMU if they wanted to spend time with me (was almost my birthday). I thought about how open-minded some of the people were (or weren't) for a while, then created a new FB and added select ones I felt wouldn't gossip about it. I already have gotten male-failed on the phone for a while.
What I'm saying, in addition to any ideas that may have given you, is that may want to figure out which of these "friends" you want to come out to... or even keep. If it's bothering you this much, you may not be ready to come out yet, or you may need some better friends that make you feel more comfortable. I understand these are only online ones, and I'm closer friends with some online people than my local friends.
So, your answer is basically a question itself: "Do I want to keep (this person) as a friend" for each person. Also ask yourself why they're important to you, because again, if you even doubt how they'd react, sounds like you could do better. For "how to come out" to who you want to, I hope what I said earlier helps!