I played AGoT back during Winter ED and with Martell coming back to the LCg, I've decided to start up again.  Here is my question:

I want to play Martell, so I know I need to grab PotS, how many though?  Also, which chapter packs are a must have for Martell?

Thanks all.

Check  website in my signature. You can see there what cards you get in each expansion (quantity is in last column).

You'd probably get a better response in the General subforum.  Not many people look down here....  You should be fine with one PotS since it has two of each card in it.  With Martell just really getting full LCG support, there aren't really any solid decks with tournament success to cite to support buying one chapter pack or another.  My guess would be that the Scattered Armies pack would fit the Martell vengeful theme pretty well.  I've also heard good things about Lost Oasis and Vengeful Blade so you might consider A Time of Trials and The Battle for Blackwater Bay.  Ancient Enemies (for the Fury plots) and Refugees of War (for the refugee cards) are two other packs that contain cards for each house allegiance that many people like.

A Song of Summer also has 3 cards with good overlapping uses of summer. You could also look at City of Secerts (for the city of Lies plot and Shadow of the South, denying opponents ability to play events can be big). I also like Tower of the Hand as Dornish Paramour and Hand's Judgment are 2 of my more liked cards.