I was asked this question by a reader by of my e-newsletter (Link to sign-up). When I first started practicing magic at 16, I didn't have a teacher. In fact, I self taught myself. Right from the beginning, I'd replicate the instructions on how to do different packages, from different books, but once I "got" the concept, I would start to experiment with the practices and concepts, to see what else I could do and also to personalize the practices to enhance their effectiveness in my life. I did and do a lot of learning of how other people approach magic. I think it's essential really, because you can't begin to personalize your own approach without understanding what other people have. This is why I emphasize having a broad foundation to draw on, so that way you get a variety of experiences and practices to temper your own perspective. But I also think that just sticking to what other people have said or done leads to stagnancy, so you need to be willing to test and experiment and personalize what you learn, and after a certain point, also depart from what you learned and actually develop your own practices, based off your own ideas.
Experimentation occurs alongside the foundation building practices. As you learn and practice a particular technique, think about how you can change it and adapt it. What would you do differently and why? Then try out your variation and see what happens. Respect the foundation, but test it as well.