Well I'm pretty sure I'm not the best teacher in the patreon department, but as I said, I think the most important thing is to have an audience already. One which you can offer something extra in return for their support. As a blogger, I guess it could be something topic related. Like... if you're a food blogger, you could offer your patrons some behind the scenes footage, maybe some videos. Extra cooking tips, QA sessions, that sort of thing.

But I'm really just pulling this out of thin air, or atleast talking back to you what I've read online. The best advice I can give you is to check out other successful people on patreon who are in the same line of business you are. You can check what they offer their patrons and see how they advertize their page. Maybe you can learn from that :-)