Salesforce Trailhead has just released the ability for anyone to create their own personalized learning journey called a Trailmix on Trailhead. I have created a companion Trailmix for this course, which is available here: https://trailhead.salesforce.com/users/005500000062BWFAA2/trailmixes/mike-wheeler-administrator-certification-trailmix
Although completing Trailhead trails is not required, I do recommend that you get as much hands on experience as possible on the Salesforce platform. I have found that Trailhead is a great way to get that experience as you learn, and have found that students that supplement this course with Trailhead have a greater success rate in passing the exam on the first attempt.
You can either sporadically work through the Trailmix while working through this course, or revisit it after you have completed this course. Go at your own pace and whatever makes sense to you and your schedule. Many students have been know to go through this course multiple times as well, so you may want to elect to tackle the Trailmix during your second pass of this course. It's up to you!