It depends what you want to memorise. Method of loci is a way of making your memory intentional and controllable instead of wishy and washy. For it to work, you need to be able to break a concept down into specific chunks that can be stored and recovered to reconstruct the original concept.
That makes it great for concrete things like names, procedures, vocabulary, cards, numbers etc.
Once you get into more complex topics, the effort of breaking the topic down into chunks that can be stored easily in a memory palace is usually greater than the effort of just using your regular old memory.
However even in these cases it is a fantastic tool for memorising summaries of a complex topic. This gives you more confidence in your natural memory for the topic as others have alluded to being effective earlier in the thread.
It's not difficult to learn, visualise leaving your phone somewhere in your home and capture that feeling. Remembering where you put something extends to the mental model you have of the world as well as the physical world, it's really quite neat how your brain does this. Then all you have to do is replace the phone with some kind of symbol that reminds you of an idea/name/number etc.
And use free resources, like artofmemory.com and their forum, the core technique is so simple that anyone selling you a course is probably trying to teach you extra crap you don't need.
