Have been playing Diablo 3 for already 5 days...such a weird feeling, i love it from one side, and from other it is too much of time wasting..) Anyway, it is quite an actual question, about money in DIablo 3.
Auction, don't waste your time and money on selling cheap items, not legendary or rare kind. It is quite obvious that offer is increasing.
When you are searching for some item, using "max price for a buyout" option can you help to find what you are looking for, better. Don't forget to make sure that "has socket" option is on the list.
About the socket, i am talking about it as a person who has never played Diablo 1 and 2 properly.. , so socket is for Gems, which will increase your awesomeness, believe me!.)
Open http://us.battle.net/d3/en/item/gem/ to see the list of them and theirs' attributes. For example Ruby for weapons is the best (Monk), increasing its attack by several heavy chunks.
About the auction.
While setting a price, for example of something for 15,000 (buyout), set starting price around 1,348, which would look like if somebody bid on it.
Obvious, but worth mentioning. When you are fighting with some bidder on an item you are trying to win, use rule of 7 seconds. 7 seconds before an auction ends, bid on an item, in average plus 10 -15% of its price, it should be higher than all other bidders bids.) Sounds funny)
My recommendation is to make an accent on Magic Drop skill, the higher level increases, the better drop! I am fighting in Diablo 3 with a ring i picked up.
And have patience, buying bracers for all the money, if it is a big sum is not very rational, i am sure that waiting for an hour or two, it will be possible to find an item you want.
Have to go to work tomorrow.../)