That’s a pretty big question, which depends on your location and pest pressure. I would say you probably need only one spray over the dormant season. That is, a spray to control peach leaf curl (google it to see what it’s about). A copper spray (like LiqiCop or Kocide 3000 will work, as well as any product containing chlorothalonil -i.e. Daconil, Fungonil, ect.).
Beyond that, I would say you might hit the trees w/ a general fungicide next season. This will protect the fruit from various fungal pathogens (scab and brown rot mainly, but will also provide some impedance to the spread of canker). I use a various battery of fungicides throughout the season, but I’m a commercial grower most likely with more fungal pressure and a higher standard of fruit quality required. Some of the fungicides I use are Captan, Topsin, Indar, Bumper (propiconazole), Pristine. You would not need to spray at a commercial level.
For a more thorough discussion of what you might need as a backyard orchardist for pests in the East, you might look at a couple of topics in the Guides section of this forum.
There are plenty more threads you can search on this forum regarding pest protection (including fungal pests) but those two thread should get you started. There are lots of experienced folks here, which should be able to answer any questions you have.