While cloning is a way to see how someone has built their project and practice on your own, I don't recommend it as a best practice outside in the real world. There are plenty of courses online that teach development by having the student build projects which are in essence "clones". Many of which the student has extended and used as a springboard to advance their skill set. However, to be good at what you do and go "pro", you have to do much more. Knowing why and how the project functions is much deeper than the surface knowledge of building the clone.
Then there's the legal side of things. Intellectual and Copyright laws are in place for a reason. There's real money associated with someone's project and cloning it without prior consent could get you into trouble. Yeah, there are templates for free and for sale that you can use. These assets are provided with the proper license agreements that make it safe for you clone, copy, modify , and redistribute.
To be good ... study, experiment, break things, fail and fail again, fix it then break it again. Ask for help until you no longer need to ask, keep studying, and celebrate your victories. Do all of this and remember to have fun.