There's no minimum order
Its second-best feature is to double the triggers from the doctors abilities, so The Tenth Doctor can get plenty of Allons-y triggers, while The Ninth Doctor can get an extra upkeep, and so on
So, as long as you find a way to get more cards into your discard pile for Roaring Moons devastating attack, youll be good to go
Note that costs paid to activate the ability, such as sacrificing permanents, discarding cards, or losing life are not countered
That said, between ramps ubiquity in Commander, the fact that ramping one land for 2 mana has been good enough for many cards to see consistent play in the format for years, and the risk that Deep Gnome Terramancer will be a dead card is minimal at best, and Id call it a safe bet youll come out ahead far more often than not when playing this card
Instant speed tutors are incredibly rare, though you don't get the card until your next turn