There are enough choices to make one's head spin! There are a lot of free software, and a lot of ones you pay for. The Adobe CC subscription is VERY good, including both LR [choose LR Classic] and PS, with a few other things thrown in. You can concentrate on learning LR first, as it has a lot of editing features, and a lot of people use it exclusively. Once you feel fairly competent with LR, if you decide that you want to use features in PS, then tackle that. I used LR for several years before feeling limited by it, and when the subscription came out I jumped right in because I wanted to use "layers". The best way to get into PS is to take it step by step, tool by tool. There is too much there to try to learn it all at once!

There are various other programs that can be used as "plug-ins" which many use because they offer some things that are either different from or better than what is found in LR or PS. But in general, the Adobe CC subscription may be all you need.

Most programs offer free trials. I recommend starting with the trial, so you can search around and learn how it works, before starting to pay. And moving from the trial to the subscription is quite easy. And remember, no matter what program you choose, there will be a learning curve, so if you want the best software for editing, in my opinion the Adobe CC subscription is the way to go.

Hope this helps.
Susan

Photoshop has been around since the late 1980s, so it's been through many revisions and rewrites. It's a collection of hundreds of highly refined tools requested by millions of users. It even has its own ecosystem of plug-ins to enhance it. As such, it is impossible to learn it all in a lifetime, because as soon as you think you have it all, they revise it!

No two users will need the same feature set, either, so it's a matter of picking and choosing the tools that work for you, and learning others as your needs grow. I started with version 1.x, and used 3, 4, 6, 7, CS2, CS3, CS6, and the last few versions of CC. If you decide to use Photoshop CC 2018, look for online tutorials. There are many, many good free resources on YouTube, and on sites like http://www.jkost.com (Julieanne Kost's site... she's an Adobe Master Trainer. I've taken three of her live seminars. Her videos are excellent.).

Lynda.com, and Kelby One are also good for paid tutorial help.
Assuming you have asked yourself, is optimizing your images your goal? One thing I would advise before signing up for tutorials or even getting a Post Proces. program is to get your good shots organized on your computer. Have them ranked as to the best and have some projects in mind. For example, for some you may need to just correct exposure or make a sunset deeper. For others you may want to add blue skies to some landscapes, you may want to fix the background in several shots, open someones eyes in people shots, add type in another, etc. Knowing what you want to do is not a small thing. After 20 years in Photoshop, I can almost achieve whatever I want to but the thing that is still the biggest challenge for me is coming up with the good image and the good idea and knowing the difference.