Ask HN: Help me come up with a pricing model

Hey guys! I want to launch that site https://www.candlapp.com/ (which is a personal tracker for book readers), but I still can't figure out the pricing model. Some of the questions I ask myself are: 1) Should there be a free layer? 2) Should I provide several plans (for different set of features), or just one "subscription" fee for everything. 3) I kinda feel, that $2.99 is a reasonable price, but I also feel that $9 would be more realistic in terms of enough revenue to keep afloat. How do I estimate it?