Find out the popular and heavily in demand items. Watch their average prices for a while, and buy at a low price and sell at high or average price. Try to to buy too expensive items, so in case of loss you won't lose much.

I recommended the BSM items (75,71) humanian items, crafted fang items, 61 fang items, glyph(60,56) crafted 55 items, 50 shadow items, 32 green ice, reinforced/expert, and event items.