Hello there! I like this question a lot actually. When questioning what to believe, look inside yourself. What do you *feel* to be true? Sure anyone can read up on ideas of life that have been passed down by individual people, but we all have our own individual truth.
Just explore all the various ideas without worrying too much about having a "set" grid of beliefs. Whatever resonates with your heart, is your truth.

And then you will indeed find that what you believe is a blueprint for how you will live your life. The amazing thing about life is that it is malleable, we can shape it and make whatever we want out of it, when starting with the way we look at it.