OK so there are quite a few ways here are a few I use a lot.
Go to Qubba buy crude oil then go to Hara and sell it. Then buy A LOT of fuel, I usually go with 6000 or 8000 L. Then go to either Sekir Bashka or Abu Kirdyk and sell as much fuel as you can. If you have cars keep like 2000 or 3000 L, sell the rest and then leave town and wait for about 5 days. Go in and you should get a lot of gold. Take that gold and go back to Qubba and sell the gold at Qubba. Take crude oil and go to Smerd. Sell it and buy alcohol. Sell it at Qubba. Do that till all the gold in Qubba is used up. Buy all the jewlery you can see in Qubba, then sell it around other cities. I make about 900k or 1m everytime.
(From Whirled): Another, safer, method is to stay within the Qubba area. Going to Sekir Bashka and Abu Kirdyk is rather dangerous due to swarms of bandits (at least until you get rid of the robber base). But this way is faster anyway. Basically, the method is to buy fuel at Smerd and Hara, buy Medicines at Fort Goks, buy alcohol at Smerd, get Textiles from Okaidi, then head to Qubba to sell all of it. Then repeat. Of course, each route will vary. But the biggest money maker in my plan is the alcohol, so make sure Smerd is always a pit stop. *By the way, nearly everything except for crude oil and leather sell at ultra high prices in Qubba, even jewelry and gold if there isn't much of it. That's why Qubba is the last stop where you sell everything you've brought. In theory, however, Jewelry is the most profitable item. The only hindrance is the fact that it's hard to find large sources of Jewelry at once. After Jewelry, shoes are great. They earn a lot per unit if brought at lowest price and sold at max (Lowest: $21, Highest: $110). *Great tactic is to ferry shoes from say, Caganel to Verdamnter Platz.