Cheap Mordheim Collection

The warbands featured on this list and their status (official, unofficial, experimental) is taken from Mordheimer.com. My suggestions on which box(ex) would be ideal to purchase are based on my own tastes, what comes in them, and if they can build an actual warband by themselves for at least the first battle or two. Some of these could cost more then their mordheim specific counterparts but in all cases you'll get more flexibility in what each model carries.
At the moment there is still a lot of warbands I haven't made a post for. Some warbands are very hard to decide on like the Sisters of Sigmar where there are no real substitutes that keep the same look and feel.

Official Warbands

• Averland Mercenaries
• Beastmen Raiders
• Carnival of Chaos
• Cult of the Possessed
• Dwarf Treasure Hunters
• Kislevit (Mercenary)
• Marienburg Mercenaries
• Middenhelm Mercenaries
• Orcs & Goblins
• Ostrander Mercenaries
• Reikland Mercenaries 
• Sisters of Sigmar
• Skaven
• Undead
• Witch Hunters

Unofficial Warbands

• Amazon Warriors
• Bretonnian Knights
• Dark Elves Warband
• Lizardmen Warriors
• Norse Warband (getting their own post)
• Pirate Crew
• Pit Fighters (getting their own post)
• Shadow Warriors
• The Outlaws of Stirwood Forest (getting their own post)
• Tomb Guardians

Experimental Warbands

• Albion Barbarian Tribe
• Assassin Squad (skaven)
• Circus Extraordinaire
• Druchii Warband
• Halfling Warband
• Mordheimers' Fanatics
• Night Goblins Warband
• Ogre Warband
• Wood Elves

Suppliments

• War Dogs
• Hired Swords 

I am not associated with Games-Workshop, the cheap Mordheim project is purely for making the selection of boxes for starting a new warband easier for those who want to get into the game without using the limited range of models specifically built for them while still being made by GW so they can be used in GW hosted events like at my local bunker.