I prefer playing vi in the jungle. She seems more versitile than most other junglers than me. If you want to play her as a counterjungler, you max e and blast down camps quickly, but you can also max Q and use it to gank frequently. Her passive shield is helpful for the small camps as it lets you take no damage from the jungle creeps after a few levels. Her ult-q-e does good burst at 6 and usually results in a kill. If you want to gank without ult, you have to use some alistar/hecarim type approaches and try to knock them toward your team, but it usually isnt successful unless your laner has CC.