I checked the AH mostly for tradeskill recipes as I lvl'd Enchanting on both chars; only bought reasonably-priced recipes. I rarely bought gear but if I saw a good TWIN set of capes or chests that would last me awhile(eagle gear mostly) and it was priced fair enough(fuck 5g for a lv18 cape/cloth chest) I'd buy 'em. Up till outland though again, I rarely bought gear off the AH, though since my 70's an LWer I made a few pieces/cloaks for them as they lvl'd cuz they did take hits occasionally and also started helping DPS post-30.

At 57 however all bets're off...if you can find a matching set of good gear on the AH at a reasonable price go for it. That's the lvl Outlands gear starts dropping, yay for Of the Sorc/Invoker/Elder suffixes! If you looted mobs as you lvl'd and SOLD things on the AH as you lvl'd you should be fine moneywise to hopefully buy an epic land mount by 60 too.

I did the above and had about 300ish gold by 60 on BOTH alts; I borrowed the remaining cost for epic mounts from my Rogue who got rich doing SMV quests he hadn't done pre-70 & the alts had Exalted with Stormwind thanks to the Lunar Festival Elders giving good rep(even my 70 isn't Exalted with any Alliance yet and both my alts were Exalted with SW by 52 lol); since the patch gave you a Discount at every rep level instead of just Honored like it used to be, I paid 40g less for Epic Riding in SW than I did at Darnassus, and that's why my alts have horses and I have a cat ;p

That said, I had no more than 20s between BOTH alts after buying that. At lv62.5 and with an AH still full of goodies, I have 400g on both alts again already.(Though I don't remember if I've trained skills since 60 =x) Just loot EVERYTHING you see, sell the greys(some get up to 1-2g on their own), and that's with BOTH alts being Enchanters, selling any greens that won't go on the AH(Boar plate, non-eagle/monkey/elder/etc stuff) for 2+g, DEing anything below 2g and still lvling enchanting. Sell cloth, sell greens(both to vendor and AH depending on the item and it's popularity), and do every quest, even the collection quests past a certain lvl, more grinding, more loot to sell :p

Also once you're high enough or even if you already have a 70, solo Scholomance; tons of Large Brilliant Shards, easy to clear groups, and the Teachers/blue spirits up front drop Enchant Weapon - Lifestealing frequently(I've had 4-5 drop in 2 runs before, they upped the droprate in a post-bc patch), and misc greens aplenty + dark runes if you're a mana user which can come in handy or be sold for crafters/raiders(And raiders value darkrunes highly for being an extra +mana cooldown besides pots)