"easiest" is a bad term to use. Some people are good at some things, some are good at others. Look at missuse's TC here:
http://forum.toribash.com/tori.php?username=missuse
That's all from marketing, not texturing.
In-game methods like tourneys are easiest for those who are good in-game.
Marketing (buying/selling items in the market - see below for links) is easiest for those good at haggling.
Texturing (making and selling textures) is easiest for those good at art.
Market links:
http://forum.toribash.com/tori_market.php
http://forum.toribash.com/forumdisplay.php?f=371