Biddulph
keep your options open and your scope wide- just looking in markets and charity shops you can learn a lot more than dealers who may not be specifically interested in beads, and in such conditions whatever catches your eye that costs little may then turn out to be desirable and possibly valuable so look regularly -dont ask for beads by name that are known to have a high value... after purchasing you can do more research.
in London UK where i live i just take some chances and often end up with extraordinary items of interest...there are antique, ethnic and craft fairs where you can handle items before buying.
my most recent collector's book shows many many beads of all materials and ages in my own collection- almost all discovered at low prices .
(send me a private message if you want more details)-