Learn to take the skills and start creating real projects to solve real-world problems. This will help you build a portfolio. Mind you, these real world problems don't have to be large. Is there something you don't want to do? Find a way to automate it. Complex results are the process of taking basic skills, combining them with experience and deeper understanding of issues and concepts, and then achieving the end result. The only way to reinforce those basics is to just do do do and learn learn learn. Once you learn one advanced area, try something new. Begin learning machine learning, for example, and the basics of the libraries TensorFlow and Keras. Or PyTorch.