Generally, though it could vary slightly depending on the expansion, the Set Booster would contain twelve cards, comprised of 1 to 5 cards at Rare or higher, then a selection of Commons, Uncommons and a bonus 2 non-playable cards too
Youll want to either cast this after your creatures have been deployed or have a way to put counters on them, as it doesnt continue to put counters on creatures when they enter the battlefield
The real kicker here is the activated ability, which will end up putting four +1/+1 counters on two creatures you control
Based around scrying and casting high value instants and sorceries, Elminster's static ability reduces the mana cost of the next instant or sorcery you would cast by the number of cards you looked at the last time you scried
Sure, it may only be half the card drawing of something like, say, Mulldrifter
For example, if an opponent loses 1 life and then gains 2 life in the same turn, you can cast a spell for its spectacle cost that turn