First Ebay can be a treasure trove of items if you find the right lots. I have built three armies at the same time for the cost of one from the stores.
As people have pointed out repeatedly, the free company box is best for duelists. At the same time you will get spare bits for other things.
If you want light cav with either hand weapons or bows, easy to take pistoliers and swap bits from free company set. Something I have looked at doing is using goblin wolf riders as light cav. The stats are not to different, can easily say, fluff wise, that they are gobos that have overcome their fear of elves, squabbling nature, and anything else that would make them gobos... There is also the hobogoblin special unit that also isn't that different from goblin wolf riders. Plastic kit, likely to find cheap on ebay at some point, get DoW light cav with spears.
Common pikemen conversion is empire state troops with either lengthened or replaced spear shafts, a conversion I am planning on doing soon.
Cannons covered well, either dwarf cannon or modified empire cannon. Note on galloper gun, expect to pay apprx $30 usd or more for them from ebay, high demand. (speaking of, if anyone has a gun and crew, but not bronzino, pls let me know)
Also, easy conversion for paymaster bodyguard, state-troop body guard with pistolier head. Right paint scheme and this looks awesome! I will post pics of mine eventually.
Also any mounted kislevs work well in a DoW army, the list even references them, although they are not cheap on ebay.