Don't buy any 78xx there are fine replacements, and you dont need 100 but 5 pcs. will do for the start
I have to agree with this, the 7805 really is a hot, power hungry, dinosaur, and the are far more efficient options that are quite cheap, like the L4940V5.
edit: buying a resistor and capacitor assortment can be a good idea, doesn't have to be anything specific, just look for a cheap assortment on ebay.
As for other parts, I would recommend just ordering a few spares when you order parts for your projects, as it will be very specific to what you like to make, and how you like to make it.