They look amazing. So happy for you and I know they will do really well for you. Cannot wait to see them bloom.
That gravel will be fine when screened as you are doing. My sources for products seems to change all the time when I go in to purchase. Going to look into getting Horriculture Pumice.
Thinking of adding some pelleted composted chicken manure or something alike. The Thai and folks in Australia and India use it.
Rinoa, usually sends quite nice size plants (caudex's).
Rick