Magic defense should be the least of your priorities. Shellra V 5/5 with pants gives you 29.2%, whm job trait of magic defense 6 gives 20%. That leaves you with just .8% below that cap which is found on any iLvl piece.
If you use gearswap you can tell it to have different sets for day and night, fit the serp gear in accordingly.
I find magic
evasion to be a really nice stat and it keeps me alive for things like Yorica delve.
Sanare Earring Flashward Earring Felicitas cape +1 and augmented alluvion armors.
As for pdt the typical dark rings, umbra cape, twilight torque, and earth staff will have you at 43% during the day, 49% at night; +4% to everything with defending. Easily capped off with augmented alluvion feet/hands to swap out with the serp gear.