which is your recommendation pls?

tokina 11-18mm?
canon 10-18mm?
sigma 10-20mm ?

for my canon apsc sensor. new to landscape.

Canon 10-18mm is the cheapest of the lot. Best bang for your buck.

Get the Tokina if you really want big aperture (for i dunno, astro photgraphy?)

tokina 11-16

Canon 10-18 should be cheap and good eliminating out reasons to buy Tamron 10-24 and sigma 10-20. Canon 10-18mm is the best buy for its price.

Other lenses like Tokina 11-16mm and Sigma 8-16mm are pricier but have special features. Tokina 11-16 having the widest aperture, which is favored by video, but every mm counts in UWA so 11mm is not the widest lens. Sigma 8-16 having the widest UWA focal length for Canon Crop system.

Since you're new I recommend get the Canon 10-18mm.

And don't forget the Canon 10-18mm also has IS, which will help with video too.