Deck Concept: Flood the board with a huge amount of skeleton tokens and force your opponents to deal with that - you should get card advantage automatically and hopefully win out from there, especially if you get one of your token boosting cards out. Necromancer as an avatar's greatest strength is the ability to turn mana into useful tokens without expending cards, and 
and 
have and respectively, which can help you get a *lot* of tokens out without expending any spells in the first couple rounds (potentially 5 tokens by turn 3 at no card cost if you're able to play an open X on turns 2 and 3). You should strive to take advantage of as many of the 1 skeleton tokens as you can as long as it won't cause you to otherwise waste a lot of mana for the turn, because even if you're not getting high cost cards out on curve you'll be preserving your card advantage. Likewise I threw some of the and , , and for even more board presence from sites to push this concept as far as I can get it to go
Key cards: , , and are all great ways to make your swarm of tokens scarier.
Funny cards: can be cast from the graveyard repeatedly in the same turn if it keeps dying, so you can use it to throw skeleton tokens at things an extra space away for 1 apiece as much as you want. can become a huge problem for your opponent if you're able to park it somewhere near where your skeleton horde is fighting and dying.