Be experimental. A lot of people tend to gravitate to videos or tutorials – but you’ll get a whole lot more out of reading a good book. Learning and fully understanding all the tools at your disposal within any program will make your decisions throughout the process more calculated.
Your portfolio items look great and it looks like you’ve been experimenting with different approaches / styles already. Try reaching into different media for awhile – painting, 3D rendering, coding, etc. – then see what you’re able to pull back into your Graphic Design. Every artform has something to learn from its siblings.