http://www.midsouthshooterssupply.com/item.asp?sku=000308208
Those 250 gr Shockwaves should shoot good, here is a better price on them for you. It is hard to say what the rifle will like actually. Also the Knight Red Hots should shoot well, and you can try some XTP's as well.
As for the powder FFg or FFFg that is the grade of powder. FFg will work fine for you in the Knight. The way it works, FFg is for rifles and shotguns from 50 caliber on up. FFFg is for ,50 caliber and below. Many people shoot both grades of powder in their rifles.