Do you have any suggested or preferred miniatures? I feel like GW Brets are an obvious choice, but I unfortunately don't have any...
Viewing post in Of Knights & Quests Revised Edition comments
Bretonnians by GW would be great! I personally have bought a couple of boxes of Northstar Military Figures' Fristgrave Knights, which is a good price for ten plastic knights per box with a more adventurer aesthetic and tons of weapon and customization options.
Perry Miniatures also sells boxes of both foot and mounted knights, with the Agincourt knights being very flexible and extremely affordable.
Lastly, the original rules were written and playtested with 2" tall knight toys bought in a $10 tub!
Yes, Citadel minis are fantastic, but they really are a large financial investment. Secondhand markets might still be good although current releases have doubtless spiked the prices. The Perry twins sculpted a TON of stuff for Citadel over the years, and their current kits are a bit more realistically proportioned (the weapons are the actual right size but feel weedy), but otherwise it's like working with GW kits again!