What do I do without a mentor to guide my career?

You are trying to build a career without anyone ahead of you lighting the path. No mentor, no guide, no one whose experience you can borrow when you are unsure which way to turn. So you are figuring it out alone, and it is slower and lonelier than it should be, and you feel the lack of it. The absence is real and it is a genuine disadvantage, so do not pretend otherwise. But notice one thing, mentorship is not a single wise elder who adopts you and shows you everything. That picture is rare and it keeps people waiting for someone who never comes. Real guidance is usually gathered in pieces, a bit from this person, a lesson from that one, an honest half-hour here and there. So go and assemble it rather than waiting for it to find you. Pick one person you respect and ask them a single specific question, or for one coffee, not to be your mentor for life, just to help with one thing. Most people say yes to that, because it is small and it is flattering. Do that a few times and you will find you have built, piece by piece, the guidance no one handed you. You do not need one mentor. You need the courage to ask several people for a little.