As a beginner (with or without basic knowledge) it’s important to build a solid pianistic foundation through a well-structured piano method. I recommend Faber & Faber (for children and adults) or Hal Leonard (for children and adults).
I mostly use Faber & Faber which consists of several levels. You can work through all the books in a few years, depending on how much time you invest.
After that you can decide depending on you stylistic interests, where you want to focus (Jazz, Pop, Classical, Improvisation, etc…)
You do not need to buy anything for the first lesson, if necessary I’ll recommend a suitable piano method book for each student individually. To save you time and research, I always offer to buy the necessary materials at a local music store and then pass them on for the same price.
In general you require between 3-5 books per year. The costs are not included in the price for piano lessons.
You can find a repertoire selection here.