質問: I'm trying to say "blessed with many talents", but I am not sure if I am using たくさん correctly here. I am thinking that 「たくさんの才能に恵まれている」 is more grammatically correct but I can't think why. Maybe because たくさん is both an adjective and an adverb, and thus whilst 「たくさん飲んだ」(drank a lot) makes sense, 「たくさん恵まれている」(be blessed a lot) doesn't sound so natural.
回答: Yes, 才能にたくさん恵まれている is natural. Dictionaries say たくさん is a na-adjective and noun, and often used as an adverb. たくさんの才能に恵まれている and 才能にたくさん恵まれている are natural, but I think the latter is used more often. For example, I feel 図書館にはたくさん本がある is more common than 図書館にはたくさんの本がある.