It depends largely on how you define "philosopher."
I've been a deep thinker (i.e. philosophical) all my life. However, I didn't begin seriously studying philosophy until fairly recently.
I'm arrogant/confident enough to believe that I can make some contributions to the field in a few areas. But my ideas aren't published yet and will probably never be widely circulated or accepted in academia (which I have limited respect for).
I'm working on a book about philosophy right now. Rather than call myself a "philosopher," I'll probably narrow the field to calling myself an expert on "applied political philosophy," or something like that.
I'm going to include a fairly detailed biography that covers both my strong points and weak points and let readers decide for themselves how they want to judge me.
There are some fairly well known and widely published philosophers who are nothing but quacks.
In summary, if you're going to introduce yourself as a philosopher, just take care to explain exactly what you mean. If you're an unpublished student of philosophy who's working on a degree or a paper, then that might be helpful to know. Your age and life experience can also help people judge your qualifications.