It is not about luck , it is about quantity of mobs you need to kill and loot. Basically any mob that spawn lesser magic things can spawn such ring. Including imps at champ spawn.
You better combine your search with something else : training pet's wrestling or your toon weapon skill , training one more imbuer with unraveling , looking for clean splinter weapon , gathering spellweaving scrolls, collecting imbuing essences in SA , try to get thinkers legs, etc. Without such additional tasks this grind makes no sense.
Then any mob spawning several items can be good for you. Troglodytes are just easy target with only physical damage. Easy to kill , easy to get slayer for them.If you want such ring /bracelet fast - earn gold somewhere else and buy it on VS.
Below is result of 1-hour pet training today in painted caves. 125 luck , Tram.
1 catch with 5% SSI and overcapped DEX (10) . And a bracelet leafblade ninjia or thrower can possibly use.
View attachment 139747
View attachment 139747