My lowest tier is just for those that want to support me, nothing new. You will be surprised how many people will subscribe for a couple of pounds to support a favourite writer.
For higher tiers I offer exclusive content I don't post anywhere else. I know writers that offer, advanced viewing of content or copies of their book when it is released. Even the ability to ask a question and get that question turned into the inspiration for a post or unique art work.
Jump on there and see what people are offering and see if you can get inspiration from there.
It has taken me about 18 months, but I make three figures on there now.