You get the most entries from reading Marriage Games, but you can enter without reading.
If you'd like to read books in my voice that are similar to The Games Duet, I recommend Songs of Submission. The story is complete from how-do-you-do to HEA.
As the books were released in serial format, I suggest the bundles as your most economical option.
If you're on Kobo, the first eight books are available in an eight book bundle.