I just bought the pack a couple of days ago and have been realy enjoying the game so now looking to expand my fleet. I have a question regarding the upgrade cards, If I would like to field 3 xwings with the shield upgrade do I have to buy 3 YT-1300 expansion packs or would just one be enough?

Each YT-1300 expansion comes with two shield upgrade cards.

However, you don't *really* need the official cards. You can just make your own, or write it on a slip of paper, or whatever. That's a lot of money to drop just to get a couple of cards. :-P

You do need the actual cards, however, for official tournament play. From the Tournament rules :

During tournament play, each player is required to use components included in official X-Wing products
with the exception of third party maneuver templates and range rulers, use of which is addressed below.

Ship, base, and card proxies are not allowed.

Imperial Aces is supposed to come with 2 Shield Upgrades as well when it is releases at the end of the year.

If you're going to play in a FFG snactioned event, like the Worlds, then yes you do. If you don't plan on doing that, then use proxie cards.

This is true for things like Shield Upgrades or Wedge.

Seeing how hard it is to find the X-Wing and Tie Fighter expansions, I'd have no issue with someone useing a proxie card for Wedge.

Relating to another thread if you can find someone who has purchased multiple X-Wing and/or TIE Fighter expansions you may be able to get his/her "extra" unique pilots. If you've got one Wedge you really don't need two unless you're going to do something to your card or play mirror matches against yourself. While that could work for the unique X-Wing and T/F pilots it doesn't work as well for the other things.