I feel I should skip around a little bit and explain how to make money in Jita. Jita is the most populated hub in the game, and pretty much is the center of the Eve-Universe. This means that miners and industrialist will usually come to Jita to sell everything, and this means you can buy a lot of stuff quickly. Players will go to Jita and fit whole ships because it is convenient and cheap.
All of this means that 90% of the other people in local are other traders. Competition is absolutely insane, and in some buy orders will be over cut in under 5 minutes. There is a lot of profit to be made here, but the margins are TINY. The key to Jita trading is taking advantage of what it does best, high quantity of trades. You have to move massive amounts of things to make a profit on the low margins.
WARNING: Price can change FAST, and that profit can disappear before you can resell your stock.
This is where most traders will tell you to find something to trade in, by starting at the top of the list and working down. I figure I can do a lot better. I will tell you what to trade in and why. I just cant tell you specific items like hulks, because I have no idea what price hulks will be. I will tell you groups and some generalizations about them.
Faction Ammo - Low Risk, Slow Moving, Medium Margins
Faction ammo prices are pretty stable, and they have nice margins. The problem is the fact that they are relatively slow moving, especially when you are trying to resell your stock. People generally don't buy more then there pvp or mission ship can hold.
Moon Materials - High Risk, Fast Moving, Decent Margins
Moon Minerals are probably the most dangerous thing to trade in eve. The competition is the worst, and you will be over cut in minutes. You have to trade in rather large amounts to make any isk. You will want to layer your orders so you can get around the 5 minute lockout time. The profits can be pretty insane.
Planetary Materials - Medium Risk, Medium-Fast Moving, Decent Margins
Planetary Materials are like the little brother to moon materials. You have to trade in large amounts, competition is pretty bad. The only thing is NOT all planetary materials are really profitable. You will want to focus on pos fuel.
Faction Ships - Medium Risk,Fast Moving, Decent Margins
The nice thing about faction ships is that you can really easily see the profit. Trading one ship will net you a profit of 5m-20m, if not more. The taxes and fees can be rather steep if you do not have the proper skills.
Ships - Medium Risk, Medium Moving, Questionable Margins
Ship margins in Jita can be so small that you will lose money on fees, but it can be possible to make a profit on good deals. Just keep your eyes open.
Modules - Low Risk, Slow Moving, Questionable Margins
The key with module trading is to jump on the good deals. Find things that have high margins, buy up a lot and sell them slowly over time.
Skill Books - Really Safe, Slow Moving, Really Low Margins
I consider this brute force trading. Buy up the skill books at a NPC station, and haul them to Jita, Since Jita has so much traffic it won't be uncommon to find someone that will want to buy one or two. The price is set by NPC, and as long as you don't sell below npc cost you will be fine.
Attribute Implants - Low Risk, Medium Moving, Low Margins
You will want to find implants that have some sort of margin, but it still possible to turn a profit.
Other Implants - Low Risk, Really Slow Moving, High Margins
This is a bit of a generalization, but you can make nice margins on certain implants. The problem is that the turn over time might be a week if not longer.