If you decide to take an exam without taking the earlier exams first, you may find it more difficult than it would be otherwise. So recommend taking exams within the same subject in a row so you can take advantage the overlap of information. With that being said, here is the list of CLEP exams by order of difficulty with from the easiest in level 1 to the most difficult exams listed in level 5. Please keep in mind this list is based on my personal experience so it will may vary for you.
Level 1 – easy to pass with 4 hours study time
Introduction to Sociology – 3 Credits
Information Systems and Computer Applications – 3 Credits
Analyzing and Interpreting Literature – 6 Credits
Human Growth and Development – 3 Credits
Level 2 – easy
Principles of Management – 3 Credits
Principles of Marketing – 3 Credits
Introduction to Psychology – 3 Credits
Introduction to Educational Psychology – 3 Credits
English Composition w/Essay – 6 Credits
English Composition w/o Essay – 6 Credits
Freshman College Composition – 6 Credits
History of the United States I: Early Colonization to 1877 – 3 Credits
Level 3 – moderate difficulty
College Mathematics – 6 Credits
College Algebra – 3 Credits
History of the United States II: 1865 to the Present – 3 Credits
Social Sciences and History – 6 Credits
Humanities – 6 Credits
Natural Sciences – 6 Credits
American Literature – 6 Credits
English Literature – 6 Credits
Biology – 6 Credits
Level 4 – Difficult
Precalculus – 3 Credits
Principles of Microeconomics – 3 Credits
Principles of Macroeconomics – 3 Credits
Introductory Business Law – 3 Credits
American Government – 3 Credits
Financial Accounting – 3 Credits
Level 5 – very difficult
Chemistry – 6 Credits
Calculus – 3 Credits
Western Civilization I: Ancient Near East to 1648 – 3 Credits
Western Civilization II: 1648 to the Present – 3 Credits