How do you have so many legendaries if you just started, card packs? Anyhow
Ice Block isn't good. Think of it this way: take cards that will prevent you from losing instead of losing one turn later.
I prefer Arcane Explosion over Arcane Missiles; it scales better with spell power, at the downside of not damaging the hero. I prefer the board control, as it can potentially 1 for 3+ if you have even one spell power minion on the board.
Azure Drakes are really good for mages imo; it gives card draw immediately as well as offering spell damage.
You don't have Flamestrike, which is all but necessary for mages. The board control it brings is unmatched.
Gurubashi is another good card for mages; you can activate his damage ramp with your innate Fireblast, making him a huge threat that always demolishes or demands premium removal.
I think you need more threats in your deck. Currently your lategame minions consist exclusively of Sylvanas and Malygos. Both of these are good cards, but they will be removed almost instantly because very little in your deck screams for the opponent to use Assassinate, Shadow Word: Death, etc. Adding Gurubashi helps in this imo; he can draw removal to protect the legendaries, or carry in case the legends get removed.
You also need to add taunt to your deck, otherwise decks that aggressively target the face will bowl you over, especially those with weapons. Adding a second Blizzard can help with this, but Sen'jin Shieldmasta offers good defense with good trade potential for a reasonable cost. You can also look into higher power taunt minions; these are less cost efficient but may work with your playstyle. I don't like them for mage as best case endgame turns for me are generally play a minion + cast a spell, which is more difficult to do with high cost taunters.
Another point for Arcane Explosion: it gets rid of Blood Imp guaranteed (unless there are two, in which case use spell power). Missles can miss, leaving you with no answer until 6.
These are all just thoughts; use some, overlook others, and keep evolving your deck. Pay attention to what works, what has little impact, what sits in your hand, and especially which cards force the opponent to spend 2 or more to get rid of them, or give you an extra (like Azure Drake and Thalnos). Good luck!