It's Europe as others have said where the improvement has been astonishing - the league form given the spend was always likely to take them close to Celtic, even though the way they are currently running away with it has shocked me, in a good way.
As has been said, they went from losing in EL qualification to Luxembourgian part-timers, to last season where they beat Feyenoord, Porto (including getting a draw in Portugal) and Braga before coming a cropper against Leverkusen, a Champions League perennial. That was a seriously impressive run that raised a few eyebrows.
I'm surprised no one paid the money they wanted for Morelos, he got 29 goals in 47 appearances last season, fantastic numbers. I suppose his disciplinary record and lack of record in a bigger league put people off given Rangers want around £20m.
Stevie's doing a grand job so far to be fair.