Budget Zoolock

Kobold Librarian

This deck plays more like your traditional aggro deck than most warlock decks. As a result it is nessecary to have both solid low cost drops as well as draw options. Kobold Librarian provides both of these and is generally a very good 1 drop card.

When facing aggro decks you must  establish and maintain board presence.

Voidwalker

As such, Voidwalker provides a solid 1 drop with taunt that will deter and/or halt your opponents early game progress.

Demonfire

Demonfire serves the dual purpose of buffing friendly minions and acting as an early game removal option.

Hooked Reaver

Hooked Reaver might seem like a late game card, but this deck already contains several cards that damage your hero and aggro decks only expedite the process. As such, it is not abnormal to reach 15 health early in the game. And if you do, a 4 drop 7/7 with taunt is a massive tempo swing.

Control decks are always one of the tougher match ups for aggro decks. As such, your best chance at beating an aggro deck is to buff minions before your opponent has the opportunity to remove them. Against these decks you also want to show restraint so that you can play multiple larger cards at once so that your opponent cannot remove all cards at once.

Soul Infusion

This card allows you to give a minion +2/+2 before it even hits the board. This allows you to buff minions on turns before you play them so that you can drop multiple minions in one turn.

Void Analyst

Void Analyst works to provide a wide range buff to cards in your hand. Buffs such as this are twice as effective when applied to cards like Doubling Imp.