Please find below a list of G adjectives which might be used to describe a person.
Positive
gifted
good
great
Negative
gauche
grouchy
grumpy
Other
gabby
giddy
gregarious
There are other lists of adjectives on this site. For more adjectives starting in G, see this post containing a good number of adjectives beginning with the letter G, some of which can be used for describing people.
Graceful