I haven't really done any transitioning between genres, I prefer to be an all rounder than stick to few ones. But starting a new genre will always be the same. At the current time of technological advances, there are some amazing youtube channels you could follow. An Alpha Collective member that I enjoy his work and taking to is Nate Luebbe. He make some amazing, inspirational work. Another is Matt Kloskowski, when he's not chasing wild animals, and Drew Geraci. I could fill the entire forum with names, but inspiration photographers' work is what you need to see, analyze and use to make your personal shot list. I also recommend following and looking at images from National Geographic.
You already have your feet wet and understand a lot about photography from the genres you shot, you only need inspirations and assignments to get you going.
I think building your portfolio is the best start. Showing off your skills in landscape photography will certainly help attract clients and partners. A mentor of mine told me I needed to become a sort of "go-to" person for the niche I wanted to shoot in, that takes a lot of time but it gave me a goal to work towards.