One of my best friends is named
Katherine, and she goes by
Katy, so I have a positive association with this name, though I much prefer the spelling
Catherine.
Kathryn is also a decent spelling. It made several comebacks in the late twentieth and early twenty-first century, so it's not dated yet.
As for
Katie, it's not a bad nickname, but it has a childish or teenage feel that doesn't exactly work on adults. I much prefer
Kathy,
Kitty, or
Kat, though
Katie,
Kate, or
Katy are not bad at all.
Katie as a a standalone name, however, just seems childish. I do not care much for the
Kaitlin,
Kaitlyn, and
Katelyn alternatives to
Caitlin that use
Katie as a nicknames.