Cost of a Disciple

So lately I have been spending a lot of my time wondering about salvation. What it really means to be a christian, what the price is to follow God, if there even is one...here me out and tell me what you think..

For months this has been a real struggle with me, I look at the way I live my life and I sometime wonder why God saved me. Then I look at my school and wonder why so many people claim to be christians and live the way they do (I mean here me straight in NO WAY am I saying I have this all figured out and that im perfect! But I realize my sin and I work on giving it to God and overcoming my weaknesses). It makes me wonder if saying a simple little prayer when you were younger is enough. Is that all you do? I mean God gives you grace over your sin, so is it good enough to get "saved" and then keep living the way you want to live and hoping God's grace will cover it?

That thinking is justified by the thought that their are two levels of christianity; level one being just that, you asked