The first principle to follow is always go through the MANUFACTURER'S SPECIFICATIONS or INSTRUCTIONS before starting any flooring or dado works.
In general a substrate of cement : sand ( 1:4) or (1:5) is good enough as a bedding mortar base, and generally we lay the tiles in cement slurry which can be about 0.5 by weight of cement i.e 50 kgs of cement x 0.5 = 25 litres water is generally used it may go up to to 0.60 ( 30 litres ) based on the slurry consistency which can be derived actually on site conditions.
Nowadays the use of TILE ADHESIVES is sensible as due to large scale use of vitrified tiles bonding is hampered due to the use of cement slurry and tile adhesives are a better option to cement paste.
For Dado a thick paste of cement mixed with water is prepared by masons this too again depends on site conditions, however, i would suggest the use of only TILE ADHESIVES for all types of dado works. we can also ensure further adhesion by applying the adhesive with serrated trowel both on the tile and the surface to be tiled one day in advance. This will ensure better bonding of the tiles with the substrate.