I would like to make four playable decks (at the same time) using the core set. How many cards would I need to add to do that?

Also, for a while at least I'll have to make the decks from my CCG collection. Are there any specific suggestions for what cards or type of cards to add to each of the decks?

Thanks in advance for any help.

Are these four player decks intended to be for joust or melee?

If melee, the core set decks are actually pretty fairly balanced, assuming each player knows what each House does best and then plays to their strengths while keeping an eye on the other guys board and power total.

In Joust, Stark needs intrigue. Add inexpensive guys that will help fill that out. They need draw (well everyone but Lannister needs draw, Targ is okay if you are playing an attachment deck and running Xaro's Home and Lady Daenery's Chambers).

Baratheon doesn't need much, maybe a few more inexpensive guys to help with flops and act as claim soak until the larger guys with renown hit the table.

Targaryen just needs you to settle on a theme and keep the cards relatively focused.

Lannister needs some military strength and power, though not much of either.