I'd say don't worry much about the fast glass. You're going to be taking photos of things that are standing still, and you're probably going to have plenty of time to do it, AND you're going to want to be using smallish apertures to get the scene focused. Tripods are therefore the order of the day here, and if you're using a tripod and want large DOF, fast glass is pointless.
Worry much more about:
1) Having a good sturdy tripod that you like using
2) Having a good quality ND filter (maybe a 3 stop one and a 10 stop one, or a NICE QUALITY variable one). Almost all landscapes tend to look good with somewhat long exposures. Water blurs into a silky, attractive glassy sheet; clouds blur a little bit at 30ish seconds+ which has a very cool and calm effect. Mist will look dreamier, etc. You may also want to take normal, shorter exposure images, but the long ones are the ones that require the equipment you need to worry about more so. In other words, short exposures are either going to be handheld during the day mostly, and won't require much fancy equipment. OR they will be an afterthought once you've already set up the tripod for a long exposure shot. Just change settings and remove the ND and snap a shorter photo before taking down the setup and moving on. Neither short exposure situation requires any particularly special equipment. It's not like sports. (I'm assuming you don't also want bid photos, in which case that would change things significantly)
3) Make sure to always turn off image stabilization on a tripod.