Actully you can make a twink with no main. First you get some
gold by just questing or asking or ninja.... Then you get the money and make a AH alt who sits at AH and just buys stuff
like Ace, two, three of anything and sell for a tiny bit more
Then you keep on doing that( which can get boring)until you have money then you Buy HIgher lvl items and sell for alot more.
Then you keep doing that and you will finally make some money
Some things to Look out for on AH:
Gems.
Plans(Black smith, Enchanting etc...)
Twink armour.( i got sentry cloak for 5g and sold for 80g)
Senty cloak
Magefist gloves
and if ppl say WTB XXXXXXXXX
look for XXXXXXXXX on AH and then sell to them higher then what you brougt :D
And how i know this.
My freind who is the 2nd best twink i seen
for lvl 19 rouge Souljaboi his main is only lvl 11
For 19, there's not much you can do at this point beside run VC a couple times to get a few blue items. I strongly discourage going for the 19 bracket, since you will be competing against people who could spend 1300 gold like the poster above.
For 29 or higher, my advice is to 1) research quests and dungeon drops on this site, to find the gear in the level range that is the best for you, and 2) take up two gathering professions, like skinning and mining, or even three if you do fishing, and sell everything you get on the auction house. Use that money to buy some decent greens to fill out your armor once you get to your level, and for enchants. Don't waste your money on anything else on the auction house (for instance, don't buy lvl 22 armor if you are on your way to being a 29 twink) and try not to die while leveling so that you can save as much money as possible.
Once you start PVP-ing, you can save up your marks of honor to buy better stuff from the PVP vendors.