There are at least three ways of improving spellcasting. Onomancy, Rune Craft, & the following more miscellaneous information.
Glyph circles could be a layer or a spell, which determines the conditions a spellcaster is trying to overcome.
It is the main reason rituals are a thing; spellcasters are trying to cast a higher version of some existing spell, putting down all of the variables mean a spellcaster has to put down a ring of incantation for each of them. This typically makes the spellcasting a ritual, adding time respectively to the casting.
For example in application, making "Enlarge/Reduce" last an hour instead of a minute is one ring of magic. Making "Enlarge/Reduce" enlarge a creature by 2 sizes instead of one, is also one ring of magic. It would take a higher spell level per ring, in this case fourth tier, and at least ten minutes of casting. In theory, concentration can also be removed from a spell in this manner.
A pretty good indicator would be the spell casting done in godawful "spiderman nowayhome" where casting a spell to have people forget, each ring Dr.Strange makes is another condition he's adding to the spell.
Wax itself can be enchanted with a spell, or made from herbs. Alchemist or artificer stuff. Burning of it gives effects given imprinted on them as a delivery method, poison also being applicable. Make the poison into the wax of something so as it burns nobody is the wiser they're being poisoned. Probably offers disadvantage to that saving throw. If dosed over a period of time.. that would be Insidious.