I am a theist, what do you think of my proof for God existing?

[Homeless Nutter]

[...]
What do you think about my proof for the existence of God?

It's nonsense. First of all - if you decided, that everything has a cause, because you see a lot of causality around you - then who/what caused god? And if god can exist without a cause, then so can anything else, meaning there would be no need for god/first cause.

Secondly, even if your reasoning were sound - it's not very satisfying, compared to the multitude of claims related to your imaginary friend. There is nothing in your "proof", that your "first cause" "operates" anything. If you want to call the first link in the cause/effect chain in the universe "a god", then so be it, but that god would be pretty useless to you as a theist, longing for a sky-daddy. In fact it could very well no longer exist. It may have started, or "created" the reaction (like the Big Bang), which produced all the subsequent ones and led to the development of our universe, but its job is done. You provide no evidence, that your god is present anywhere in the universe and if you look around you'll see countless examples of causes that seized to exist at some point after starting an effect, so by your "logic" - god is most likely dead.

So you have no reason to believe in the afterlife, or that god knows/cares about you, or anything else for that matter. No reason to believe, that god is anything like you. No reason to believe, that any god revealed itself to any human,  that there's any way to know god, or it's will, if it has such a faculty. No reason to believe, that any holy books are anything more than ramblings of madmen. No reason to believe, that your god interferes with the reality at all. 

You're not a theist - you're a deist at best. Your god is no better, than no god at all.