How often you will need to spray and what product you use is up to you. It will depend on how much time you want to allocate to this task, how much insect/fungal damage you are willing to accept (or not) and what the weather is for that growing season (weather often can play a large part in the severity of many fruit diseases).
You don’t want to spray?
Then consider going organic and growing your fruit in bags.
Willing to spray but not too often?
Then try and hit the KEY times to spray for prevention of a major pest issue.
In the case of apples, they key times are May and June (Primary apple scab, plum curculio, leafrollers, 1st generation codling moth, cedar-apple rust). The second key time on apples is for apple maggot (historically the peak flight is in August). So, the key times for apple pest control would be to spray all of May—June and then once in early August. Will this give you perfect fruit? Possibly not, but it should give you a crop of decent apples most years (depending on the severity of sooty blotch, fly speck & second-generation codling moth).