I am currently lvl 20 and have made about 19 gold total (it is kinda neat that it shows you that in the market screen)... I just say that because I don't know if others are making more or less, and it kinda qualifies all the rest of the stuff I am going to say here.
I loot everything. I harvest, collect, mine, fish, gather, etc. everything I can get. I am a pack rat. This will give you something to sell to the vendor.
When you do this you run out of inventory room pretty fast, so consequently, much of the first money I made, I spent on getting larger bags. This allowed me to collect and loot more stuff.
Loot sells to either vendors or other players in the market. But the harvested, gathered, collected, etc. things are mostly sold to other players on the market. All (or almost all) are used in the tradeskill system someplace, so someone will need it. There are somethings that some people always need. There are somethings that will sell often.
Knowledge is power. I used trial and error to find out what things to always collect, or somethings that I don't make money on, I destroy.
When putting thing up for sale on the market... I have a couple different strategies. When I really want to get rid of something, I tend to sell it well below the price of everyone else (but becareful not to go below the price you could get from a vendor). Other things I sell I know will sell eventually so I put the price a bit higher. Most often for the average Item I sell it for either the second highest price i see or just below the second highest price. (this allows people to buy the cheapest thing, which will happen... then I get more money from the next person who buys the stuff.)
I also leave my computer on and sell as often as I can. When I am playing with my kids or working around the house or watching tv... I have my player in market mode. I have upgraded my computer so that I can alt-enter and minimize EQ2, and then do other things with my computer while my char is in market mode.
Working the market and collecting all this crap is not easy. But by lvl 21, I have gained enough money to upgrade all my spells to Apprentice III or Adept I, and purchase bags o plenty to collect all the crap I want.
Note: on my server - Crushbone - the boiled leather backpacks sell for less than then boxes. although the boxes often have 2 more slots, it also weighs 100... research the weight reduction vs slots vs price.
I don't know if the way I do things is the best or not, but this is the way I do it.
I also know that other people make a lot of money by doing tradeskills. I have not enjoyed my tradeskill experience so far. but I know I have given a lot of money to people who make backpacks : )
Okay, i think I have spent enough time typing... and the servers are back up again after the morning take down.
enjoy