Copper Zen said:
Stay away from 4th edition--The makers acknowledged it sucks and are working on the 5th edition.
Actually, it was Essentials which led to the early retirement. Evidence, before Essentials, 4e was leading the charts. Also evidence, the Essentials team don't know what the fuck they are doing. Also, WotC are not known for consistently sound and sane decisions. Evidence: the info released for D&D Next. Dear god, they sound like incompetent morons half the time while tossing brilliant but almost impossible to achieve plans the other half of the time.
OT: Hobby shops usually have complete sets of dice for D&D players. Normally, assuming you're providing all the dice (so players don't have any of their own) for each person you'd want a d20 and about 2-3 of all others. OK, that might be a bit excessive but 1 d20 per person is pretty good, you can also do with 1 per 2 people. For the other dice, go with about 2-3 per 2 people but get more d6s, especially if you'll be rolling stats. Just go with 4 per person for those, or if you're poor (or just don't want to lug that many dice) - again, 4 per 2 people is fine. If you find you need more dice (one person needs d10s, for example) just buy more - players can share for a session or two. Or they can go buy some themselves. And I don't know if it's obvious or not but get pencils - have 1 per person and some spare ones. You could do with less but don't be cheap. You can do with less rubbers (or "erasers", you American, you). Actually one trick I do with rubbers is to just separate them in halves or quarters (depending on how big they are) - that way I get more of them (seriously, has anybody here wore one out?) and I can share or afford to lose them without much problem.
Book-wise, you
could roll with the Player's Handbook only, but you'd probably want the Dungeon Master's Guide as a new DM - it has...well, advice for DMs unsurprisingly. It's not
mandatory but it's recommended if you're new to RPGs. Even then it's not that necessary if you have ideas for a game already and just want some rules to bind them with. Also, there is the Monster Manual - it is really handy. At the very, very least, you want the MM so you can just pull enemies from it at any time. There are books with complete adventures, too - if you don't want to make your own and aren't bad (at least the...two I've played. not till the end even). Treasure was...I forget, I think you can find some equipment in the Player's Handbok but I can't recall if it's all (so, for stuff like generic enchantments for items and so on) of it, you may need the Dungeon Master's Guide - I'm not sure. Do note that you can use the d20 SRD [http://www.d20srd.org/] which is the rules for D&D for free. It's all the rules you should need, however the Player's Handbook is still more structured - I'd advise getting that if you feel unsure.
What is the expansion set you plan on getting? There are loads - from settings to books with new rules and stuff. I'd suggest the Tome of Battle. Pick it up and, if anybody wants to run a vanilla "warrior" type class, just slap them with the it then hand it over and make them use it instead. The classes there are approximately seventy bajillion times cooler than just "a fighter". Also, a personal favourite of mine is Complete Psionics. If I were running a game, I'd just have all magic users use those rules instead (although, I could just still call it magic and get rid of some of the psionic references).
Other than that, remember rule 0 - the DM is always right. Make sure your players also know it. But don't abuse it, too - the rule that supersedes rule 0 is "you're there to have fun", rule 0 is supposed to support that. And one VERY important thing - you are not friggin' babies (at least I assume you're not) - for some reason DMs and players alike manage to forget that on a regular basis and act immature. If there is a problem, talk to the players. If somebody does something dickish, don't go passive-aggressive on him (injure or otherwise his character) in hopes "they'll get it" - it doesn't work, it never has, never will. Instead either bring it up on the table or after the game or something. This is the stupidest mistake I've seen and keep seeing being made - the "don't act like adults" mistake.