Personally I'm using a combination of Instant Ocean sea salt + reef crystals. Seems to work pretty well. I know there are others that are like against Instant Ocean and you can certainly get higher quality salt. But for me the cost difference vs. the parameters end up being negligible. Also, given current shipping non-sense I can get the Instant Ocean stuff from Amazon in a couple of days vs waiting weeks. My parameters in tank seem to be pretty stable and even though IO touts you can use tap water I'm still doing RODI for the mix. I typically do 2 cups sea salt and half cup reef crystals in a 5 gallon bucket. ALk hovers on the high side, around 11ish but this seems to be stable and is slowly coming down with regular water changes.
I use plain IO and use the money saved to buy kalk and a couple trace bottles. I don't like my alk as high as others mix up to so rather than messing with new water I keep it simple. It works great for my tank, 250g fully mixed. Lps one side, SPS the other. Last water change was 9 months ago.