There may not be a stock exchange in Orgrimmar, and there may not be a floor of day traders buying Wool Cloth futures in Ironforge, but as I mentioned last post, inflation is slowly but surely eroding the value of the gold piece with every quest turn-in.
Gold is always nice to have--you can't beat its fluidity, and it's certainly embarrassing to be caught short when your raid summons the Field Repair Bot. It's nice, but is it the best?
Gold, like paper money in real life, has no intrinsic value. You have the guarantee--of the vendors, of the government--that those numbers on your screen or on your bill can be traded for goods and services. The quantity of goods and services buyable with a given amount of gold varies depending on how much gold there is. (If you've been reading the other posts, I /sorry for repeating myself.)
So while you can't beat the ease that gold provides, it might behoove you in the long run to set aside a percentage of your money and invest in commodities. By that I mean items which (preferably) stack, have a relatively high value per unit, and are always in demand. A low vendor value is a plus, because it means you'll spend less listing it on the auction house. For the reason that they are in steady demand (and have a vendor sale price of zero), many savvy players will pick the Auction House clean of enchanting materials that are priced significantly below average, stockpiling them for a rainy day--or a day that finds the AH devoid of that particular material. Suddenly those stacks of Dream Dust that were purchased for 5 gold a stack when the market was flooded fly off the AH at 15 when they're all gone.
Equippable items generally do not make for good hedges, because of their extremely high deposit costs and sporadic demand. For a lower-level newbie, ores and cloth are good bets; the ratio of vendor value to potential AH price is very lucrative. Here's a rough idea of what to stockpile and unload on the AH at just the right moment:
Linen Cloth, Earthroot, Copper Ore, Moss Agate, Low level green items (Alts with big bankrolls are perfectly willing to shell out 1+ gold for greens with the right stats and level requirement)
Wool Cloth, Fadeleaf, Vision Dust, Tin Ore, Iron Ore
Mageweave Cloth, Gromsblood, Nether Essence, Mithril Ore, Jade
Thorium Ore, Dreamfoil, Golden Sansam, Eternal Essence, Illusion Dust, Large Brilliant Shard
All Outland herbs, mining loot, and enchanting materials. Aldor/Scryer rep items, and Coilfang Armaments.