JEgan712, It might be the saddle, if you are dealing with a decent bike shop have them check to alignment of saddle and handlebars. Your seat might be tilted as well and that is causing more discomfort than it should. As you have already seen, there are plenty of saddles to choose from once you are sure the seat is in the right place.
I think a spare tube, patch kit, pump and a multi-tool are all good initial investments. As the year heads into fall you might consider a light that can clip on to your helmet so that when the ride you start to enjoy the evening turns pitch black you can still see. Since it sounds like you will be riding only when you feel like doing it for fun you can skip fenders and racks, which won't be of much value to you. As you ride further and longer you can worry about all the other add-ons as you feel you need them.
Enjoy the riding and the exploration posibilities a bike opens up.