Check out the fantasy section of the forums and it'll be a great help to you. I know you said your BF is going to help you but the poster above me does have a good idea to get you started.
To be honest, you cant just pin down which army is the "best" or "worst". If your told that Ork's are the best, and you pick them just because of that? Well, you just might not like the play style that they are and get tired of the game without really giving it a chance. Warhammer Fantasy and 40K both require some research before hand. If you just pick one because someone said it's good, chances are (IMO) that you wont be happy.
It's all about how YOU want to play. Like ranged (bows for example)? Then you'll want an Elf army. Want to slug it out with some swords/axes/etc.? Orks, Dwarfs, those are the type you want. It's all about how you feel that you want to play the game. Once you decide how you want to play, what would "fit" you, then it's alot easier to pick an army. Btw, the same goes with Warhammer 40K. Figure out your play style, what appeals to you, then you can easily pick your army.
P.S
Welcome to the forums!
P.P.S
Edited to add this link:
http://www.heresy-online.net/forums/showthread.php?t=34330
That link will take you to the Fantasy board and will give you ALOT of info to help you choose. Good luck!
