Where should I start (from a business owner perspective)?

Hello all! I am lost when it comes to SEO. I am usually good at DIYing, but I don't think I can start down this rabbit hole! I rather turn to someone who has skill. But we are a small startup, so cash flow is tight. I was wondering what we should start with first if we were to spend a little cash. Like what would get us the most mileage to get us started with SEO?