Ten gates were released with that Magic set, one for each of the 10 Ravnican guilds (Izzet Guildgate, Orzhov Guildgate, and Simic Guildgate, and so on for each color pair), each of which enters the battlefield tapped and taps for 1 mana of either of the guild's colors
This makes all of your Rats much better in combat, forcing your opponents to trade their creatures if they want to block a Rat, which will then give you more Rat tokens as another creature dies.
As such, every kind of deck archetype is playable, and there is no shortage of them
However, in most cases, a 40-card deck will provide more consistency in drawing your best cards, and I would prefer that over a diluted 60-card configuration
It has some sacrifice cards, other cards that reward you for having black creatures or a bunch of Swamps, removal, and a few demons