Welcome, Lori! I'd start with her Tudor books, maybe The Lady in the Tower or The Rose without a Thorn.
With some of her series books, it is better to read them in chronological order. Here's a list here (some of the books have been republished under new titles):
http://jeanplaidy.tripod.com/id18.htm
If you like romance, do bear in mind that Plaidy's novels aren't particularly romance-y--more just straight historical fiction.