Most landscape photographers don't use ISO 400 film. The exception would be chromogenic C41 black and white type films, since these are very fine grained when exposed well. What do you want to show with your images? How large? How detailed?
If you're doing landscape work, then be prepared to bring a tripod. That means you can shoot ISO 25, 50, 100 film and work out what you like best. If you're shooting ISO 400, you won't get the detail of the tones and textures recorded as vividly as with ISO 50 film. Many photographers do do this (in the UK where the weather's great for ISO 400 film!).
Here's a selection of what's popular with landscape artists (BW) nowadays. It has changed a bit from say, 10 years ago I presume you're using 35mm format.
Easy to find:
fine grain:
- Ilford Pan F+ ISO 50
- Ilford Delta 100
- Fuji Acros 100
- Arista 100
- Agfa APX 100
- Kodak TMax
- Lucky! film
medium grain:
Ilford FP4+ ISO 125
Kodak Plus X ISO 125
and slide film:
- Agfa Scala
Harder to find:
- Efke 25
- Maco UP 25
- Maco Orthochromatic 25
- Kodak Technical Pan (25)
- Agfa APX 25
- Efke 50
And specialist film:
Kodak HIE infrared
Konica IR750
Maco 750, 820, 850aura or c versions
I'd recommend starting from the top and working your way down to the bottom. The film types get harder to work with as you go down the categories. You could try it the other way wrong and post some results here......
Learn how to use contrast filters (yellow, green, orange and red) to squeeze out the most from whatever emulsion you have.
Good luck.