As for fox, try watching Amsa's matches. Backing away Fair is a good option, egg lay is also good for it's range, since good foxes will try to outspace you. DJC Counter Nair OoS / Usmash OoS are also good options since our shield is so good. Just make sure you counter his Nair or Drill, not the shine.
CC is also a awsome weapon, use it along dsmash.
As for setups, at low % try landing that grab and getting an uthrow>usmash, at mid % go for dthrow>dsmash. Pivot grabs are your better options, but learn the right range for dashgrab.
Remember that dash attack is good, especially at edgeguarding spacies trying to get back from below.
Utilt is awesome, and setup juggles and another utilt (utilt, utilt, djc uair, keep the juggling)
Go for stages with many platforms, you'll need them for the movement, practice wavelanding as move as fluidily as you can.
Also, watch out for those usmashes, especially shine>jcusmash. Do not try to get out of the shield too early.