What's the next step? This book has given you the necessary foundation on which to build a much larger understanding of Ruby and computer programming. You can now begin to dive into "real" problems without being bogged down by the basics.
If you are studying with Launch School, you will soon begin breaking down problems and developing solutions in Ruby using object oriented principles. The things we covered in this book are the things that must be automatic to an everyday Ruby developer. If you aren't to that point yet, don't panic. You can review these concepts by reading through the suggested articles in the "Optional: Other OO Resources" section of Lesson 1 in the Object Oriented Programming course.
From here, Launch School students should continue to review and expand upon what you have learned by working through the next lessons of the Object Oriented Programming course. Also, don't forget to take advantage of the Exercises resource provided by Launch School! The collection of practice problems in the 120 - Object Oriented Programming section will provide you with an excellent way to continue practicing the concepts of object oriented programming.