Deulofeu scored one goal and set up another in the Toffees' 2-0 Capital One Cup quarter-final win over Middlesbrough on Tuesday.
Asked how good he believes the 21-year-old Spaniard can be, Martinez said: "As good as he wants - that's a big part.
"Gerard is a young man in terms of the amount of games that he's played at this level, so he needs a lot of games. But as a natural talent, he's as good as it gets.
"He's got that talent that you dream to have, he's got the talent that anyone would pay for a ticket to watch him."