i have 3150 ip, its was difficult to me to save that ip, so im wanting to know who is the best champion of 3150 ip, i like katarina, akali, pantehon, kassadin, karthus, nidalee, what of these champions is the best?

well i dont know your play style or anything but off the top of my hat ide say pantheon.
all of those heros are fantastic and fun to play so whichever you choose im pretty sure you will have fun
but pantheon is a great hero to play and a bit less squishy than the rest, and his ult is fantastic for starting helping or changing any fight on the map =]

or if not pantheon ide go with katarina, a fantastic assassin very squishy but can deal amazing damage =]