First, in keeping with its theory, there is no best or single method for studying A Course in Miracles. It is a curriculum undertaken by the student under the guidance of the Holy Spirit or Jesus, and as the manual for teachers specifically states, the training is “highly individualized” (M.9.1:5; M.29.2:6). Moreover, there can be no strict guidelines or rules that apply to every individual, as circumstances, backgrounds, and abilities, among other factors, differ greatly.
With regard to reading and studying the material, Jesus does not say which should be done first, the text, the workbook, or the manual. That decision is up to each student. There is no right or wrong way of proceeding with the material. Yet, to attain a comprehensive understanding of the thought system and a solid foundation for practicing the lessons, students are encouraged to study the text at some point in their process.
Jesus advises us to study it carefully, but not proceed too quickly with it, lest we plunge unnecessarily into overwhelming fear (T.I.VII.4,5; see also Question #1163). Also, in the Introduction to the workbook he explains that the “theoretical foundation ... the text provides is necessary as a framework to make the exercises in this workbook meaningful” (W.in.1:1). Thus, Jesus clearly expects his students to spend time with the text at some point in their process.