I keep a couple d20's and any dice I use for damage on the table, which normally means a few d6's. When I know I'll be casting a lot, that means a bunch of d6's...
I usually get out two full sets of dice, sans the d12, which I still never use. I refuse the get the d12 out unless someone tells me I need it. Hasn't happened yet.
I usually have about two full sets whether as a player or a DM. However, I usually bring about SIX full sets with me to each game in my minis case, because there's always the possiblity that a player or two will forget their dice and need loaners.
OTOH, since everybody does the same thing, I could probably go to the game with nothing but my character sheet and be covered.
I usually get out two full sets of dice, sans the d12, which I still never use. I refuse the get the d12 out unless someone tells me I need it. Hasn't happened yet.
As a player, I usually have 2 full sets plus an extra d20, and possibly any extra dice that I might need for a particular ability.
As a Dm, 3 full sets and 3 or 4 extra d20s.
I always have 5 or 6 sets in my dice bag, for others who forget their dice or if I need a bunch of dice for unusual circumstances. And I always have a d2, d3, and d5 in the bag, just because I can.
Either way, two full sets. As a DM, though, I've got a backup. I've got a big bag o' dice to represent most NPCs (PCs get minis, thanks to one of the players). If I'm in a bind, I'll just take some of the dice that aren't currently in play.
I keep my 14 (There are two sets of 7 dice in a bag, slowly I take them out and leave them there) as I need to use them. Most of the people I gamed with doesn't have dice though....