Your lens selection for large format may end up being quite different then what you use now in 35mm and medium format. Everyone is different. Your first lens may not even end up being one that you keep. Don't worry about it. You can always sell it later for around what you paid if it's not for you.
But one lens and go out and shoot it a lot. Eventually, you will learn what focal lengths you like and don't like.
Take Ian up on his generous offer. He can help you with your first choice of lens.
This is great advice.
I own two lenses, a 6"(150mm) Petzval and a 150/265 convertable Schnieder. I was surprised to find that this has been plenty and that I rarely even convert to 265.
Mark Barendt, Beaverton, OR
"We do not see things the way they are. We see things the way we are." Ana´s Nin