Depends on the kingdom, and, for that matter, the traveller, but what are your thoughts? Mine are below, but they are wishy-washy.
Page: if there's a source of draw on the board then one page will suffice, unless she gets hit by the opponent's Warrior. Buying two feels like "insurance" against the latter possibility (and also potentially pumps up your Warrior)... something akin to opening Feast on a Witch board in base Dominion, but better. Probably the optimal number on such a board is 2.
If there's no source of draw, then Warrior acts as a lab, but you're always adding a Silver to your deck to get that Warrior, so without trashing, your net draw power doesn't change.
If there's no source of draw, but there is a way to trash silvers, especially for benefit, and there's great engine payload like Bridge or Goons, then you should gain basically as many pages as you can.
Peasant: usually I find myself buying exactly one. The Peasant pile is never a good target for a token from Teacher, because it can never have both +1 card and +1 action. Disciple is a great card, and it sucks to have to play it on a bad card (or even on thin air) to rush to teacher, and this makes you want more than one Peasant, but the deck-clog of the terminal, non-drawing Peasant, then soldier, is often just too much to justify buying a second.