Everyone reacts differently to cannabis and so what is great for me or someone else may not work best for you. That said, I can tell you what I like and what works for me for sleep. In general edibles ate a great option as they last for 4-6 hours. My preference is Kiva Terra Bites blueberries. They are 5mg a piece and depending on your tolerance you can take 5, 10 or 15 mg. Take an hour before bedtime. Another great option is Absolute Extracts sublingual spray called SleepyTime. This is fairly immediate, but I find one spray is enough for me, any more might make me stay awake!
I hope this helps!