League-of-legends – Are players listed by Elo on normal

AFAIK, the ranking only considers premade teams vs. solo queuers. Premades get higher priority (order randomized within the team), then any stragglers get randomly thrown in underneath them. This is why you end up in the bottom 1 to 2 slots so often if you solo queue for normal draft pick games - you're getting matched up with a pre-made (or 2).

I don't think that there's been any official word from Riot on this though, so this is all conjecture.

[Updated for Season 3]

The game is currently in flux (season 3 has only been out for a couple days), but with the boosted ambient gold gain, it appears you only need one gp/10. I've been building Philo Stone to great success. If you expect to get some significant assist-gold (you're confident in your kill lane, or you're Soraka and have a good eye for your ultimate), you could probably stand to buy a Kage's Lucky Pick, but I much prefer to only buy the one Philo Stone and start immediately after into my build (Sightstone, Shurelya's, Aegis -> Bulwark).

Again though, this is all pretty fresh. Your mileage may vary.

[NOTE: The answer below was provided for season 2. There were significant changes implemented for Season 3, and this answer is now out of date. It is provided here for history, but should not be followed.]

It depends. The rule of thumb is two (Philo Stone and Heart of Gold), and 98.355% of the games, you'll want those. If the game is going to absolute crap, teamfights started early and your team is getting routed, you may have to skip the second and start pouring that extra money into wards and an oracle's (counter to what you'd think, oracle's is a great purchase if you're falling behind and the laning phase is over).

I'd be very suspicious of my support if they got a third gp/5. The only real time I can see that being worthwhile is if you know it'll be a late, late game, and that you'll need to be a significant contributor in teamfights for damage.