Today's tip does not get any easier than this. No seriously they don't. People are practically giving away money to you.
I cannot tell you the amount of times that I've been on the auction house and seen gear that have the wrong gems in them. People do this because they either aren't concerned or aren't smart enough to buy the correct piece of gear for themselves. They will buy an item that has +100 Strength, +75 Dexterity & +60 Vitality (This is just an example) and they will put an green gem that will increase their Dexterity into it. This is a potential for some nice profits if you can spot it for the right price. The image you see to the right is what I have really been going after. The critical hit damage in this case isn't technically wrong, but you can put a Radiant Ruby into it and it will show up on a lot more players lists when they search for 2 handed weapons. Then I can take that same gem and put it into a piece of gear which maybe has a red gem in it and increase its Dexterity making it more attractive to Demon Hunters. As a byproduct I am then left with a red gem. Then it just continues on and on until you get bored of it then you purchase a piece of gear with no gem in it. You throw a gem into that and you are done for the night. It is almost a game within a game.
When I run across gear that's got the wrong gem in it I try to get it in the range for 5-8K gold. Then I will take the gem out. Replace it--and then put it on the auction house for anywhere from 15-30K gold depending on its stats. You will see a lot of gear that even has 2 gem sockets and just a single gem placed on it. This too is a fantastic way to flip and item for sometimes 200-300% profit. It really doesn't get easier than that. Pricing is an important issue with this method. You've got to check the current prices of items when they've got gems in them. If you are only able to purchase them for 10K and resell them for 15K it really isn't worth it. At least in my eyes it's not.
Quick side note on the subject of stumbling across high quality gems, by the way. If you've got a keen eye and are looking for it you can find people who make the terrible mistake of putting a very high quality gem into their gear and selling their gear as junk. This happens all the time as well. I don't know what would make someone do something so foolish, but it happens and way more than you would expect. In case you aren't sure what the gems actually look like here is the gem progression chart that shows the worse to best gems. The further right they go the more they are obviously worth. I am usually looking for the Square through Radiant Square gems. Reason being that those are in a decent price point where many people are buying them and they still give a large return when you upgrade a piece of gear with them. Those are the ones I've found the most.
Here is the FULL chart. It applies to all gems. Ruby is just the example image:
I have plowed through a ton of different strategies since I've begun playing Diablo 3 and I have to admit this one is by far, without question, the easiest one that I have done. I do have to be honest I didn't come up with it personally. I was working in a group with a few buddies and I gave a piece of gear to a buddy. Then when he was done with it he gave it back to me and I realized he had put the wrong gem in it to buff his own stats. It was the wrong piece of gear for him but with the high quality gem it was usable for him for the time being. When I got it back I realized the gem and he said keep it so I swapped it out, put an emerald in it and threw the ruby into a weapon and walked away with almost 50K gold worth of profits. Incredibly easy!
Be sure to check out our previous posts on the site as well including our posts highlighting the many reasons why FREE is better and you shouldn't pay for Diablo 3 Gold Secrets when you can get them free both here and many other forums on the internet!
**Article was edited. Chart that was initially linked as from an older build. My Apologies!