See Tut: -
Ultra-Wide-Angle vs Kit & Stitch, featuring a fish!
Basic point is
"More Land, does not more 'Landscape' make".
And I exemplify with a few, deliberately 'boring' shots from an 8-16 UWA and a 180 FoV 'full-round' fish-eye, and what you get with the kit 18-55, with and with out pano-stitching.
There's many ways to skin a cat, as they say. but....
You don't 'need', and in fact it's often perverse, to go 'wide angle' for Landscapes. If you go very wide, all you do is shrink subject elements in the frame so they are far less prominent and loose impact, and pack in wide expanses of 'boring' sky and grass or whatever, to even more loose your subject.
Wide angle photography is a very demanding topic, and as far as Landscapes go.. beyond the cliche of a prominent rock in the foreground against a wide expanse of desert or whatnot, it's actually VERY much more demanding than other genre's, particularly things like portrait, macro or action, where the 'impact' and interest tends to come from making your main subject element very large and prominent in the frame, which with a tele-lens the lens can almost do for you.
Eg.. imagine a chocolate box 'landscape' of cows in a field, with a river and trees behind them... and a peculiarly annoying fluorescent crisp packet of ten caught in the hedge! With a 'wide' it grabs everything that's in sight, and such 'clutter' or distracting detail you could exclude from the shot with a narrower FoV is going to get in there.
With a more 'normal' or even tele lens, the more restricted FoV is likely to clip out a lot of such clutter.... and WHO the bludy hell though that it was a good idea to put bludy DOGS in Hi-Vis ?!?! (just to vocalise on one of my pet hates!)... but the narrower angle lens will help you far more easily isolate what is the subject of interest.
So to answer the question;
start with wot-choo-got. The 'Kit' lens is as good a place to start as anywhere. It's probably as wide as you would often 'want' to go anyway, and for the few instances you may want to go wider, pano stitching offers pretty good intro into how much more wide you may need. Plus a proper pano, only stretching the field on the horizontal, a bit like a tele, tends to clip, that 'boring' expanse of sky and foreground.