In tropical conditions it is best to run salt levels at 4,000 ppm. 2 x 25 kg bags per 10,000 litres.
TRS is the salt brand and buy the red label not the blue (swimming pool salts) as the blue is the same as the red but more expensive because it is bagged for pools. Salt doesn't go anywhere, but will need toping up after a lot of rain and if you have a leak or very high bather load,
Put the salt in as the pool as its being filled. Don't turn the chlorinator on for a least 24 hours. Wait for the salt to dissolve completely.
You have no reason to have any soda ash. Salt pools have a high pH due to the type of chlorine being produced and hydrochloric acid is needed for that.
You will need approx 2/3rd litre twice p/wk. You will need to play around with the amount till you get good pH results. (7.2 - 7.6) Put the acid into a bucket with water in it and not the other way round. Then spread it over the pool.