When I decided to add strings to my list , a mate gave the 'basic' chord runs in a string of keys - Major , Relative Minor , Dominant and Subdominant - Or as I knew 'em then C Am F G /G7 etc and told me to think Paul Anka's Diana to practice them ! Got me into the idea of making the chord changes in time with the melody , though Diana in C , then G , Then F then A then D and then in E WAS a bit boring !
But more interesting than just playing the chords without a melody line !
   Then you can try doing the same tunes in different time signatures as well !!

             Best of Luck and HAVE FUN !!