Lately my goals have changed from crushing the auction house for extra cash each month to learning new markets and investing my profits from Diablo 3 back into my character. My idea is that when PVP and/or an expansion hit, I will have a high powered character to go along with my knowledge of both the gold auction house and the real money auction house. Having a high powered character will allow me to farm high level content effectively, which at certain times may be just as profitable as spending time on the auction house (or a good use of time while waiting for auctions to sell).
Two days ago I was stuck grinding in MP3 doing key runs and getting into the occasional group for running ubers, where you need an infernal machine to access the high level bosses that drop items to make a Hellfire Ring (which I'm still working on). I'm currently Paragon Level 11 and have yet to get a decent legendary drop while key farming.
Enter Gimmic Gaming's Class Guide. Markco posted on his blog about Gimmic Gaming's new guide and gave it a thumbs up, so I decided that it would be worth a shot. The guide contains extremely useful information about building your character and walks you through exactly how to spec to move up from whatever current Monster Power level you are farming.
I literally took the information in the guide and went from farming MP3 to MP6 by just changing my spec and investing a couple million into some new weapons.
I only purchased one class guide (each class guide is $30) because I primarily play a barbarian. That was all I needed and it was worth the $30 investment. I learned more in 30 minutes of reading and watching videos about playing my Barbarian than I've learned in the hours and hours I've spent playing the game.
You can get a class guide for each class for less the $100. If you play more than one class and want to learn go dominate with all of them, I highly recommend buying all of them for the reduced price. If you specialize like me, try out the guide for your class first. If I start playing another class, I'll be buying Gimmic's guide to that class before I even get started. I'll be posting results of my upgraded farming runs soon!