hey, i'm almost 30 now and i still haven't started. not for lack of desire so much as lack of support. like you, i lacked a supportive family and it took me a long time to decide to "come out" to them, which i only really did for the sake of finally getting it over with. because of my financial situation, i'm stuck living at home again right now, and i frequently find myself wishing i hadn't bothered telling my family because the only thing that's changed is that our already strained relationship is even more uncomfortable now, and the level of support and acceptance i get from them certainly hasn't grown over the years since i told them about my gender. sometimes it's in your best interests to come out to your family, and sometimes it's not. the only one who can really decide when it's the best time is you, and there are people who have started their transitions much later in life and are doing just fine--so don't think you have to rush into anything you're not ready to do, especially if you think it will make things worse on you without any benefits. if the bad outweighs the good, it might be better to wait until you've got a clear set of goals and you're willing and able to handle whatever you think the worst case scenario might be.
on the flip side, your friends do have a point: in this journey, your own well-being needs to take priority. some people will never accept you as you are, and unfortunately that can include your own family. it's one thing they'll just have to deal with, and while it's good to be reasonable and try to help them understand and show that you care about their feelings, you should never let your own take a backseat or be forgotten. this affects you more than anyone else, and it's not fair to hurt or deny yourself for fear of rocking the boat.
dealing with family, coming out, and taking the first steps can all be really hard and damn well terrifying. there's nothing wrong with being cautious, especially when you're so young. i know how bad it feels to see everyone else seemingly so far ahead, thinking it'll be too late by the time you get there; i feel that every day. but we all start somewhere, some much earlier or later than others, and as long as you're doing what makes you happy and healthy, you can't really go wrong. you've got plenty of time. don't be afraid of your family, but don't rush yourself into anything just because it seems like others are further ahead.