Life is tough until you get some better cards. Life is not easy to build with low mana. I try to focus on higher mana games when using life.
The shieldbearer and healers are a good combo to start with. You can double up your healers too.
I'd recomend buying the new healer if you can and the new life djinn if you can. They will help you win a lot more games with life at least in the short run.