PPE is just an acronym for Personal Protective Equipment. That includes anything from helmet, eye, and hearing protection to gloves, boots, chaps, etc.
Your right, definitely get the help and hearing protection first, then decide about the need for other types of gear. Chaps will generally sell for $50-70 and you can also get boots that have kevlar lining to help protect you feet and ankles.
Just keep in mind that PPE is not a suit of armor, it will not prevent accidents and it will not keep you from hurting yourself if you don't know how to use a chainsaw properly. PPE is simply like a seat-belt -- it can prevent catastrophic injury in the event of an accident.
By the way, they also sell chainsaw pants that you might find are more comfortable than chaps, especially in summer. They eliminate the need for an extra layer of clothing.
Good luck,