The 22-year-old has joined the club on loan from Nottingham Forest until the end of the season with a further option to make the deal permanent in the summer.
The former Hibs front man has failed to settle in England but he has been tipped to do well at Ibrox by Commons.
Speaking at a media event at Hampden Park ahead of this weekend’s Scottish Cup ties, Commons said: “Jason is a terrific player, he has a lot of ability. He just needs an arm round him.
“He needs a manager who is going to send him in the right direction.
“He can score goals, he can score spectacular goals but he has a side of him as well that can be a bit naughty.”
Watford boss Javi Gracia does not think Abdoulaye Doucoure's form will be affected by his omission from France's latest squad.