Photoshop is intended for editing photos. If you want to illustrate advertisement, illustrator is the tool you need….
to me 'editing' means selecting and sorting of images into a first edit, selects and finals. using something like bridge, capture one or lightroom.
photoshop is for retouching.
but then i'm a photographer not a designer so using it in a different way to a designer/artworker.
photoshop is easy to pick up if you have a good book or tutorials to follow.
i started with a beginners book for the basics (layers/paths/selecting etc) but picked up the advanced stuff from other professionals. or if there was a specific task a quick hunt around the web, although usually it was a case of combining techniques to get the desired results.