The English first person is always “I”, but there are many types of I in Japanese. Actually, which word you use represent what kind of people you are like. And of course, if you learn and speak in Japanese, you should call yourself somehow. Let’s have a look at the variety.
#1 Watashi 私
“Watashi” is the most common used to call or mention themselves in Japan. It can be used both for males and females, but for males, it sounds like a little formal. For females, this is used in a casual situation and also a formal one. However, using “watashi” to mention yourself will never disturb your interlocutor, so it’s a good choice to use this when you wonder what first person should be used.
#2 Boku 僕 / Ore 俺
“Boku” and “Ore” are predominantly used by males. Very few females use this to mention themselves, but it sounds irregular or strange.
“Boku” sounds very soft and tender. So, the man who uses “Boku” to mention himself looks (or sounds) kind or gentle, although it sometimes sounds “young” or “Immature” for the tenderness. However, this is also acceptable in a business situation, albeit not formal.
“Ore” sounds so strong and masculine. The man who uses this looks strong and reliable, but a little wild. Many Japanese man use this, but this tends to be casual and you should avoid using “Ore” in a formal or business situation.
#3 Watakushi わたくし
“Watakushi” is so similar to “Watashi” and the kanji is the same, but this is much more formal. If you have a business with a Japanese company and speak in Japanese, use this to mention yourself instead of “Watashi”. The audience will believe that you are so polite and reliable.
However, this is so formal that using this in a friendly conversation can sound strange. Of course, being polite is always good, but a real Japanese master will opt for and change how to call him/herself according to the situation.
#4 Your name
There are a few people who mention themselves by their name. It’s only about girls cases because many girls do that when they are young. But as you imagine, that is considered childish if a matured lady mentions herself by her name, so not many people do.