you should give him a talent GRAY or something like ??? (immeasurable) talent.
Which can make his talent stonger than anyone else but the downside is he has to work much harder than other to advance further.
what he needs is a treasure which can improve his talent i mean hardworking mc and all is good but blatantly making him advance rank just by saying that he was hardworking is actually very disrespectful for those who have talent and are still hardworking.