I think "best" is an odd goal to aim for in a game like this, it depends on what you want your wizard to be like as much as anything.
I like a bit of fluff in my armies/warbands. I figure that my (divine powered) Thaumaturge would have access to a lot of resources at his disposal, so would be accompanied by Templar-esque soldiers. From the plastic kit, I made two Men-at-Arms, two Infantrymen (with halberds), two crossbowmen, and four thugs. I used helmeted heads when possible to make them look more soldierly. My elites will consist of heavily armored Templars, Knights, and Marksmen. My warband will be slow but defensive with heavy armor and the Shield/Heal spells supporting them.
I have plans for other warbands, such as a thieves' guild themed Illusionist warband, with Thieves, Archers, Treasure Hunters, Rangers, etc. It will be faster and more shooty.
The Necromancer will have a mix of dregs. Infantrymen will have greatswords rather than halberds, since they aren't proper soldiers. There will definitely be some evil Knights though.
The Elementalist will also be supported by proper soldiers, although not from a religious order, as I imagine that he will be a court wizard supported by troops from his lord.
The Witch will be supported by Rangers, Barbarians, Archers, Thugs, Infantrymen (with axes?), Warhounds, and nothing with mail armor.