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)
Miscellaneous Dockside Extortionist Hullbreacher Karakas Leovold, Emissary of Trest Nadu, Winged Wisdom Prophet of Kruphix Sylvan Primordial Trade Secrets As much as Ive tried fitting cards into different sections, some didnt really fit in one of the other categories
Budget path, add those two
Using Daretti and the other Goblin Artificers to flicker Portal to Phyrexia, it can be a board wipe that gets around indestructible and gives you your opponents' most dangerous creatures to play with
Creating a 4/4 flying Dragon is way better than making a 2/2 Wolf, and the chance that you can get more from a nat-20
