I'm a native speaker, and we use "get ready" in exactly the way you describe.
Even though we sometimes qualify the phrase by saying: Get ready for [some event], that "for" clause can be omitted when the listener already knows where we are going. In other words, although get ready can mean different things in different contexts, I can still usually say:
C'mon! We're leaving! You need to get ready!
and that will be understood to mean: put your shoes on, brush your teeth, comb your hair and look presentable, etc.
The precise meaning get ready will vary, depending on where we are going. So long as the hearer knows where we are going, I don't need to add the, say, for your piano practice. For example, I have teenagers at home, so, for me, it works very much like this:
10 or 15 years ago, though, whenever I said, "Let's get ready" to my wife, that always included "Make sure we have the diaper bag!"
You needn't worry about get ready being misconstrued to mean "brace yourself for some bad news" or "get into your starting blocks." Those are very specialized meanings that people wouldn't even think about, unless they were in a situation where that would be the meaning that makes the most sense.
For example, if you wanted your picture taken, and I was holding your camera, I might say, "Get ready..." – which doesn't mean, "go put on your shoes," or, "brace yourself for some bad news." It simply means, "Get ready, I'm going to snap the picture now" – so you should probably just give me your best smile.
Best Answer
I upvoted your question because it provides a good example of how words can have overlapping meanings, and we must rely on context to determine which meaning is intended.
As I type this now, a couple people have already left feedback saying that climb implies specialized equipment and technical difficulty, while hike implies a more relaxed amble. While this distinction isn't wrong, I feel like it also oversimplifies your problem and fails to give your question the detailed answer it deserves.
Most words in English have multiple meanings and nuances, and can be adapted to various uses. While it's true that climb can imply using your hands or special ropes and belaying equipment, that isn't always the case. For example, when Doyle wrote in one of his Sherlock Holmes stories, "Gregson climbed the stair to arrest this desperate murderer," no one imagines Gregson using ropes, special boots, or safety harnesses. And when a news article says, "Byrd recalled trekking through western China on the way to hike K2," we don't expect to read about a walk in the park by someone carrying little more than a water bottle and some trail mix.
In the context of mountaineering, both hike and climb can be used to describe either perilous ascents or upward recreational strolls. My daughter enjoys rock climbing as a hobby, but I can still find plenty of images like this one on Google using terms such as "hike up the ridge".
If you are trying to make sure the listener understands you are going up a mountain for fun or exercise, I don't think choosing the "right" word between hike and climb is a surefire way to do the trick, as either word can be used for that purpose. It would be pedantic to correct someone and say, "You shouldn't have said climb; you should have said hike," and such talk wouldn't win you many points among a community of outdoor recreation enthusiasts.
That all said, Wikipedia has some interesting notes about verbiage that might be useful: