Should I learn Photoshop?

Would it hurt to learn Photoshop? Absolutely not! I say, go for it! However, if you're looking to create logos and banners, you may also want to consider learning Illustrator. Nancy OShea gave a great overview of how she uses Photoshop, Illustrator, and more.

There are a ton of free resources to start out with. I would start with a simple Google search or check out YouTube. Lynda.com is also great, but does require a subscription.

The answer to this question really depends on one's unique situation, even within the parameters you outline.  Knowledge is generally a good thing and will  allow you to better serve your clients, which in turn helps a career.  A great aspect about Adobe software is there are similarities in structure across most applications making your learning curve quick.

As others have suggested, Lynda.com is a great resource.

Best of luck. 

Other advice provided is good but will add one more perspective.

Definitely worth learning Photoshop if you're doing any type of digital image work. Besides using it to create graphics, things like resizing, cropping, colour adjustment, etc are valuable things for you to be able to do yourself.

In terms of taking over designing logos or banners, that is a skill in itself. Simply knowing the program won't mean the ability to come up with great graphic design. However, if you're already doing it by hand for instance and then getting someone else to digitise it, then definitely knowing the tool to get it done yourself would be quicker and more profitable. If the you're getting someone to design logos from scratch, and that person is highly skilled, he/she may do it quicker and more efficiently than you.

In terms of what software / skill will serve you you for the longest period, my advice is not to invest all your time into one program as it can change. In terms of skills, like what has been said before - pick something you enjoy doing, you have confidence in and will therefore get the most satisfaction. That will get the best results. Options are:

- Illustration for logos and other vector graphics - Illustrator

- Video - Premiere (editing), AfterEffects (post-production)

- Desktop publishing - InDesign

- Web & HTML5 - Dreamweaver, Muse, etc... (and non-Adobe programs)

- Web programming.......

etc....

Lynda.com is a good source for tutorials of all kinds:

Lynda: Online Courses, Classes, Training, Tutorials

They have a free trial.

My answer to point 2): I’ve watched the first minutes of the course and found some problems with the accuracy of the information at the very basic level. So it may be worth, but at least at the beginning it does not meet my quality requirements. And to say that someone talking about Ps CS4, CS5 aso at a time where CC was available is not that serious. A course on CS4 will be usable in recent Ps versions with some differences in how the program achieves what. So that is not an exclusion reason. But hearing someone talking about CS4 as the 4th version of Ps tells me, that the guy did not even read Wikipedia. That would be my exclusion reason and the advice not to trust getting a good course.

On 1 and 3): Ps (and Adobe skills in design in general) are mandatory. for someone considering doing busines in the world of graphic art and prepess. In addition Adobe is very strong in Video tools and Web applications. If you ask the one skill you would need, except the fact that still you should have some talent in design, I would toggle between Ps and Illustrator. Indesign is an important nice to have, knowing web design and having prepress skill would open you to very much of what is going oncurrently. And please do not neglet that mobile computing is high in demand, so designing for those devices is crucial for success.