This is my first time coming to Japan.
When I ate sushi for the first time, it was very delicious.
only after ...; not until ...
Used after the -te form of a verb to express that something happens only after that action is completed. Often implies a condition or prerequisite.
Only after you get sick do you appreciate the value of good health.
It was not until I became a parent that I understood my parents' hardships.
first time; one's first
Colloquial noun usage, often in phrases like 初めての〜 (one's first ~).
My first overseas trip made me very nervous.
This is my first experience.
I went to Japan for the first time.
Only after raising a child myself did I understand a parent's feelings.
This is my first trip abroad.
It was in high school that I first met him.
初めて is a general adverb meaning 'for the first time' usable with any verb, whereas デビュー is a noun/する-verb that specifically implies entering a field or new social stage.
初めて is the adverb "for the first time" used to describe an experience, whereas 初 attaches to nouns to label the thing itself as the first one.