I don't really think you really need 50-60 (although I'm guilty of having almost every color of TIRE silk 100 wt).
I would think the most inexpensive way to have the largest variety of quality threads for applique would be to buy prewound bobbin sets (at least to start):
Like this:
http://www.superiorthreads.com/shop/...ut-1/products/
Superior has numerous different prewound sets. NAYY.