Sec. 91.159 - VFR cruising altitude or flight level.
Except while holding in a holding pattern of 2 minutes or less, or while turning, each person operating an aircraft under VFR in level cruising flight more than 3,000 feet above the surface shall maintain the appropriate altitude or flight level prescribed below, unless otherwise authorized by ATC:
(a) When operating below 18,000 feet MSL and --
(1) On a magnetic course of zero degrees through 179 degrees, any odd thousand foot MSL altitude +500 feet (such as 3,500, 5,500, or 7,500); or
(2) On a magnetic course of 180 degrees through 359 degrees, any even thousand foot MSL altitude +500 feet (such as 4,500, 6,500, or 8,500).
(b) When operating above 18,000 feet MSL, maintain the altitude or flight level assigned by ATC.
Thus, in answer to your specific question, the appropriate cruising altitude in VFR flight (above 3,000 feet agl) is odd thousands + 500 feet for magnetic course 0 - 179, and even thousands + 500 feet for magnetic course 180. Your heading is irrelevant, as course is equivalent to ground track, and wind corrections can cause your heading to be far different from your course.
Federal Aviation Regulations, Part 91 (quoted above). I am a long-time pilot, aircraft owner and former FAA ATCS.