I agree with cornflake. There are two issues here, neither one insurmountable and both common with enthusiastic newcomers.
One, you're misusing the term beta reader. A beta gives the last look to a manuscript which is complete and polished, one which the author believes is ready to submit. It sounds as if what you'd like is a critique partner to help you with this first draft, and possibly later drafts, too.
Two, you're so eager to get going on this (which we totally get!) that you have arrived with your hand out, asking for our time and effort, before you've given any of your own.
My advice? Slow down. Keep writing, of course, but take the time to interact here. Critique others in the genre in which you write, and any you read. (I cannot stress this too strongly.) Get active on your genres' boards, and in the novels section. Spend a little time on a social, political, or hobby thread of interest. Get to know people a bit.
By the time you've interacted here, you'll have the fifty posts required to post some of your own work for feedback, plus people for whom you've written thoughtful critiques who are likely to return the favor. Wins for everybody.
Maryn, glad to meet you