Hearthpwn

This deck only requires basic cards and is meant for new players. I would recomment adding Mana Wyrm and Snowchugger ASAP for a better early game. Antique Healbot and Earthen Ring Farseer will also help against aggressive matchups. One of the cheapest mage decks to make is Mech Mage; so that is generally a good transition from this deck once you start getting more cards to make the deck.

UPDATE- 7/22/15: This deck is severely lacking in 3 drop minions, so I would highly recommend crafting Spider Tank; this will help both in the short term for this deck's mana curve and help you on your way to build a mech themed deck. After some playtesting, the weak links in this deck seem to be Mirror Image and Kobold Geomancer. If you are looking to add any new cards that cost 3 or less mana, I would recommend taking these minions out first.

Early Game:

Mulligan for Arcane Missiles and Frostbolt. Those are your key early game removal cards and will help maintain board control early in the game. Mirror Image is also an excellent tool for stalling your opponent and protecting your own minons. Elven Archer will help remove weak minions as well as give yourself at least a small presence on the board. Your 2 mana minions are also important and should be next priority for your opening hand. Don't be afraid to drop a Kobold Geomancer with no spells or Acidic Swamp Ooze with no enemy weapons.

Mid Game:

If the enemy has no minions on their side of the board then try not to overextend as there is a limited amount of minions in this deck. Watch out for AoE spells like Starfall, Hellfire and Flamestrike. Your 4 and higher drop minions have enough health to survive these but it is generally a good rule of thumb to invest no more than four minons on the board. Putting down your Gurubashi Berserker can make your opponent think twice before using AoE at the risk of enraging your berserker. Refrain from playing 2 health minions unless you only have one or two minions on your side of the board. If you are behind on board control try to bait the opponent into investing too many minions on the board for a devastating Flamestrike. Try to use Polymorph instead of Fireball on enemy minions because Fireball can be a potential finishing face damage on the enemy hero. 

Late Game:

At this point you should start finishing off your opponent with Gurubashi Berserker combos and Boulderfist Ogres. Your hero power and Elven Archers can proc the berserker for some surprise late game damage. If your opponent has about 10 health left, use Fireballs on your opponent's face as well as your hero power to push for lethal damage.