Who is funding and arming ISIS ?
Saudi Arabia yes, but it seems they are capturing newly-delivered arms from the USA to the Iraqi's too:
http://www.prisonplanet.com/how-the-us-is-arming-both-sides-of-the-iraqi-conflict.html
So the answer to who is arming Isis is that it's also partly the US, indirectly.
It's also worth mentioning that Isis are a particularly nasty bunch - even Al Qaeda denounced them:
http://www.thedailybeast.com/articles/2014/02/03/al-qaeda-denounces-syrian-jihadist-group-isis.html