I feel like I need to ask: how much critical should I be aiming for as a scholar since I want to get as many crit shields as possible?

Currently my melds (i343 currently with genji/lost all (aug) and carborundum gear) are sitting with primarily critical with direct hit on the items that are capped on it by default. My critical value is 1239, but I'm not exactly sure what percentage that amounts to as I feel I don't get a crit all that often (somewhere around 10-15% is how it feels to me).

Also, just to add in, my coffers are pretty trash and I don't pay attention to where I've gotten cracked clusters so materia in use is primary Mat V with like 3 Mat VI.