By a niche.
Well, more exactly I watched some anime series since I'm little, but I watched them like I watched a live-action series or movie. Like Cowboy Bebop, Noir, Library Wars, Death Note…
But in mid-2015, I decided to watch a bunch of LGBT movies. After watching Memento Mori, a Korean lesbian movie, I became quite fascinated by it. Thus I wanted to watch similar stuffs.
That's when I remembered that I watched Sasameki Koto few years before. So I watched it again, then discovered the GL community and various GL anime. Nowadays I consider Sasameki Koto as my "first anime" even if it's not technically the case, but it was my real "starting point".
I kept watching only GL anime up until I saw that there isn't much of them, thus I naturally started to read GL manga in June 2015. Girl Friends being my first one, it's also the first manga that I brought.
In the following months I extended into gender bender and BL. Few time later I started to watch some popular things, notably sci-fi, some pretty good like Ghost in the Shell, others pretty bad like Steins;Gate.
As I continued to watch/read older and older GL/BL/gender bender works because there isn't much, in mid-2016 I came across Thomas no Shinzou, and that's how I fell in love with old-school shōjo and how I discovered my fav' mangaka, Moto Hagio.
Now I'm really into shōjo, and still interested by GL/BL/gender bender obviously. But not much outside of it.