The fight was stopped in the eighth round due to a cut above Gradovich???s left eye and Selby was handed victory with scores of 79-73, 79-73, 80-72.
Selby, 28, now wants more featherweight world titles and while he believes unifying the division is unrealistic, he is keen to claim a second belt within the next couple of years.
Ukraine???s Vasyl Lomachenko is the WBO champion, Argentina???s Jesus Cuellar holds the WBA title and the United States??? Gary Russell Junior is the WBC champion, and Selby would be keen to get in the ring with any of them.
He told Sky Sports: ???I don???t know about dominating or unifying [the whole division], because there are some great champions. We have got Nicholas Walters [the WBA super-featherweight world champion] and Vasyl Lomachenko and Gary Russell Junior ??? they are all great champions in their own right.
???But I think I can be the IBF champion for a long time and maybe a unification in a year or two.
???Lucky enough, I am blessed to have these great fighters in the featherweight division. It???s one of the best divisions in boxing at the moment, so there are some great match-ups down the line.???
Selby produced arguably the best performance of his career to see off Gradovich, but he felt his display was still some way short of his full potential.
He admits that he has not yet fully developed mentally, but when he is, he feels he could take some stopping.
He added: ???When I am in the gym and there is no chance of me losing in sparring, I???m a totally different fighter ??? much, much better than what you are seeing on fight night.
???As soon as I can bring my training and sparring into the ring on fight night, you will see a great champion.
???The better the opponent, the better Lee Selby you will see. Each opponent I have been fighting, I have been beating with ease. Each level and each fighter I fight, I???m just going to get better and better.???