For the vast majority of people, Photoshop is complete overkill. You don't need it! And until you master it--which, depending on how computer savvy you are, may be quick or may take a long, long time--it will do more to hold you back than help you out.
But don't fret! There are many great alternatives out there. Here are five alternatives to Photoshop that are completely free! I use PCs and not Macs, so some of this won't apply to you if you own an Apple computer--sorry!
Microsoft Office Picture Manager
This may seem like an unusual alternative to Photoshop, but if you don't plan to do much post-processing, Picture Manager can do what you need a photo editor to do. Adjustments can be made to hue, saturation (and by turning saturation all the way down, you can convert an image to black-and-white), contrast and brightness. Those are the essential features you need for most images.
What Picture Manager really excels at is cropping, rotating and red-eye removal. Even though I have more powerful programs on my computer, I often do those tasks in Picture Manager because it does them either easier (cropping) or better (red-eye removal).
The best part is that there's a good chance you already have this software on your computer.
Pros: Super simple to use and does what little it does do very well.
Cons: Doesn't offer anything above basic adjustments.
Google Picasa is best known as a photo organizer (and that is something it excels at), but it also has an interesting and easy-to-use photo editor. It can do all of the basic adjustments plus a few that are more advanced (yet in a user-friendly format).
Picasa also has some creative filters that allow you to add interest to your images. You can replicate Holga, infrared, cross-process, etc., very easily. While I don't use these effects often, it's good to have them available for when I do wish to use them.
Pros: Very user-friendly and reasonably capable photo editor. The organizing capabilities and creative filters are a plus.
Cons: Doesn't have advanced features like curve adjustments, layers and clone stamp.
PhotoFiltre is more advanced than Picasa, but it is also less user-friendly. I guess that is the trade-off of a more powerful program. You can do about 75% of what you can do in Photoshop with PhotoFiltre, which means that it can do what most photographers need a photo editor to do.
The main limitation is the lack of layers and curves adjustments. You can, however, make some (but not many) adjustments using PhotoFiltre that typically would require layers or curves. If layers and curves confuse or intimidate you, this may be a good software choice for you.
Pros: Can do most things that you need a photo editor to do.
Cons: Not the most user-friendly and lacks layers and curves adjustments.
This is my favorite free photo editing software. Paint.NET can do about 95% of what Photoshop can do. There are professional photographers that use Paint.NET for post-processing. The only drawback is that it is a .NET program, which may be an issue for you (but probably won't be).
Paint.NET is about as user-friendly as PhotoFiltre, so there is a learning curve, but considering how powerful it is, you'd think it would be a little more difficult to use.
I recommend that you give this software a test spin at the very least.
Pros: Powerful photo editor.
Cons: Built on a .NET frame.
GIMP is the most advanced of the free photo editing softwares available. It can do 99% of what Photoshop can. It's very powerful! But like Photoshop, it's also tough to figure out and takes a lot of practice.
I would try some of the above softwares prior to trying GIMP. You might just find that one of them fits your needs perfectly. But if not, GIMP is certainly your answer. There is very, very little that you cannot do with this software!
Pros: Very powerful photo editor.
Cons: Not user-friendly.
There is no need to spend hundreds of dollars on Photoshop or hours and hours and hours learning confusing software. There are great alternatives to consider.
And you don't need to pick just one. I have all five of these programs on my computer and actively use three of them: Picture Manager, Picasa and Paint.NET (but mostly Paint.NET). Try a few of them and find the combination that works for you.