Cavs Defense

The Cavs defense was generally very poor this year. So while keeping the big 3 intact, what moves to the Cavs make to improve it? They obviously can't afford top tier defenders, but who are maybe some sturdy defenders that they could pick up?

Edit: Fun follow-up question, in a perfect world with no max cap and unlimited cash, do you think there's anyone the Cavs could get who would have a chance to slow down KD who's not currently on the Warriors or Cavs?