Hello :)
A single drop of lavender on your pillow can help. I use a few more drops in my diffuser, but I've read that too much lavender can have the opposite effect.
Chamomile (Roman) is one of my favourites, so I would also suggest that too!
Other oils: Mandarin, Linden Blossom, Clary Sage, Marjoram, Cistus, Valerian, Hops, Vetiver, Sandalwood, Lemon ~ list from 'The Fragrant Mind' by Valerie Ann Worwood