Granted one needs to have a good background in the Talmud, Halacha and Tanach, where does one start to learn Kabbalah after mastering the things stated above?
Your question is a good one and is difficult to answer for many reasons.
The most obvious being, what you mean when you use the term kabbalah?
In this time period, that word has many meanings, some more traditional and others not.
For example, all the words of the Gaonim are kabbalah. The meaning is about Torah transmission teacher to student, face to face, mouth to ear. It is not about mysticism necessarily.
Another consideration is your particular situation. You have stated on this site that you are a convert, which puts you in the category of an adult who has not had the benefit of an orderly Jewish education from the beginning.
As the Alter Rebbe explains in Hilchot Talmud Torah, Chapter 2:1, a person in your category divides their daily learning into thirds, between Tanach, halacha and all oral Torah, which includes the mystical parts of Torah.
It’s worth pointing out that the limitations you have mentioned in your question which were cited in Talmud from the time of the Tanna’im and Amora’im, are according to many among the Acharonim no longer applicable.
Most of kabbalistic material today is related to the subject of comprehending the orderly system which G-d has established throughout all of creation.
In that context, for someone in your station in life, an excellent place to begin for introduction is the book, Derech HaShem, also called The Way of G-d by Rabbi Moshe Chaim Luzzato. There is an excellent Hebrew-English edition translated by Rabbi Aryeh Kaplan with extensive footnotes. It will establish you with a solid, traditional foundation and with a long shopping list of books on the subject that you should acquire and learn as you grow in that knowledge of the Torah.