A lot of the information that the ladies have already mentioned are great. The first step to getting your edges back to health is to find out the cause of the breakage/thinning that you are having. Is your relaxed hair overprocessed, underprocessed, getting enough moisture, too tight scarf, braids, split ends? My edges (and nape) have been looking rough since last year. My problem was relaxers (but not to say that is your problem). My hair was wayyy overprocessed and I noticed it was thinning and then it all broke off. I am now transitioning for my own personal reasons as well I want healthy, thick chemical-free hair. I can say, that I try to moisturize, moisturize, moisturize. Some people use grease, oils, Surge, MTG are some ideas but you have got to use whatever works for YOUR hair. However, none of those "growth" potions worked for me. What has helped my hair is cutting all the damaged, split, thin ends off ugly, I notice that my hair is slowly growing by doing this (as bad as I didn't want to!). Cutting it may seem like a setback but I believe it will truely help in styling and speed up growth. Also, I make sure that I give EXTRA attention to that area when I put on moisturizing product and give that area TLC when styling that side.
HTH