Note: For a breakdown of all of the technologies learned in DataCamp, see Data Science Technologies: An Overview
DataCamp is designed to be beginner-friendly. While there are many languages and disciplines to choose from, some of the most popular are R and Python. It's totally fine to learn both at the same time!
Generally speaking, Python is more versatile: it was developed as a general-purpose programming language and has evolved to be great for data science. With Python, you can build web apps, games, and more, in addition to performing common data science tasks.
R was originally designed as a statistics language and has evolved to do much more. R excels at exploratory data analysis, data visualization, and other data-related tasks. In many cases, each language's strengths can complement the other's.
Once you've come to a decision, signing up for a career track would be the next best step. For guidance on DataCamp Tracks, see Tracks: Choosing Your Best Path.
There isn't a single way to complete courses in DataCamp - it depends on what you want to focus on first. If you're going to strengthen statistical methods, you can take advanced statistics courses, and if you're going to do Natural Language Processing, you will choose the Machine Learning courses that correspond, etc.
This is simply a guide -- it's totally up to you! Enjoy your data science journey!