another thing are 9-10 horse traders in your hand after the council rooms and before the last torturer of your oppenent
if the goal is just to draw as many cards as possible without playing actions then 9-10 adventures and 9-10 loans
of course in that case a single adventure and infinite blank cards would be be enough to draw infinite cards
edit: had an idea! your opponent could use masquerade to take your king's courts and throne rooms after you have played them, and pass you horse traders instead. That way you can use them on your previous turn for the durations, and he on his turn for the council rooms.
So now it depends on the exact rules used for KC/TR + duration, how many stay in play with the duration, and how many can you draw again next turn. Calculating this with the old official rules would be even harder and you would have to use some tricks to avoid having all of them stay in game, but i think the rules have been amended in that only the last KC/TR stays. Still pretty hard.
The most important cards are probably kc and tactican, so all other cards are only available 9 times at most to avoid ending the game.
edit2:
another trick to get a very small gain:
- start your turn with 4 horse traders and a secret chamber
- opponent plays a spy, you reveal and set aside the 4 horse traders and then reveal the secret chamber, drawing 2 horse traders, revealing them.
- Now you have to return 2 cards to the deck but have only the secret chamber in your hand. you return it.
Net gain-->1 card
- opponent plays a council room, you draw the secret chamber
- he plays a spy, you reveal SC to draw 2 horse traders, reveal them, return SC to deck
net gain -->1 card
You could do it again but you would need 10 horse traders for that.
You can use the secret chamber in conjunction with an opponents spy/pirate ship/tribute/thief/etc to pass all your king' courts and throne rooms to your opponent without him having to pass you the horse traders:
- he plays a thief, you reveal the secret chamber, draw two KCs, return two other cards, the cards are removed by the thief
- he plays 2 masquerades, you pass the KCs, receive 2 coppers.
- he plays a thief, you draw two KCs, return 2 coppers, the coppers are removed by the thief,
- repeat
definitely to hard for me to calculate