Efficiency can be determined simply by the reward you receive at certain mana costs (Counterspell and Cancel do the same thing, but Counterspell costs less), the total payoff you receive from a single card (Hull Breach and Decimate are both good cards, but Decimate usually covers much more ground), or the payoff you receive in conjunction with other cards (Anointed Procession makes other token production cards completely absurd if unchecked, which is usually better than adding one more card that simply makes tokens like Spectral Procession in a token strategy)
Showing 1-18 of 18 cards: "rules text: is, in, your, opening, hand,, you, may, begin, the, game, with, it, on, the, battlefield." Showing 1-18 of 18 cards: "rules text: is, in, your, opening, hand,, you, may, begin, the, game, with, it, on, the, battlefield."
Typically these are used in concert with discard effects in decks with heavy graveyard synergy as you will want specific things in the bin and wont be able to control whether you draw them or not
The prices are a little bit higher when it comes to things that are available from the Pokemon Center in the US or Canada, but I think it's worth it to buy from here whenever I can
Why the EB-05 Booster Box Matters Extra Booster sets like EB-05 are designed to maintain excitement between major releases