Not Updated For Current Season
If you are jungling, lifesteal is a good thing to use in low level. This is why you want Hunter's Call with Vampric Scepter which will give you lifesteal and an extra boost where you can get more life from minions and it will make you harder to kill(do not need to use smite on wraiths compared to pre-edit). At level 2, Hungering Strike will allow you to sustain your health in occasional bursts.
For the first two levels, go for the Wraiths, Wolves and the Golems. Next, for levels 3, 4 and maybe 5, go for the Ancient Golem, Lizard Elder and occasionally stick to Wraiths and Golems. Levels 5(optional) and 6, you can solo anything except Barron Nashor(but I'd recommend not soloing dragon until 7). Remember, never try to solo anything you are not comfortable with, especially if you are not at full health or have not gone back to buy items. Additionally, go into woods for jungling every few levels when there is no immediate threats to increase gold, experience and levels of you and your team mates.