Traditionally, a 'Low Magic' campaign in D&D usually means a combination of very scarce magical items and a rarity of full caster NPCs in the world. I.E. there is no friendly clerics/druids on every other corner willing to heal or selling healing potions, no barrel of +1 swords to be inspected and purchased, etc. Sometimes there are restrictions on the full caster classes for PCs, either through out right banning, requiring multi-classing with a mundane class, or a role-play oriented "burn the witch" type scenario. 5e makes this harder because, as others have mentioned, there are more classes and sub-classes with spells/supernatural abilities, and the martial classes are better balanced with the spell casters (so the martial classes are not as dependent on magic items as they were in past editions, so the lack of magic items are not as telling, and any difficulties imposed on the spell casters does make them suffer more in comparison).
I guess the question is: what type of 'low magic' feel do you want? Is it more of a 'Lord of the Rings' feel, where there is magic, but it is much more rare and subtle, but because the PCs are participating in a grand epic, they end up having more of these 'rare' items (mithril mail, glowing swords, star glass, Elven cloaks, not to mention a magic ring) than would be expected in the setting? Or is it more of a Conan-esque world where any magic is corrupt and evil (possibly with a Great Old Ones vibe), life is cheap, but the wine and song are plentiful?
I guess the question is: what type of 'low magic' feel do you want? Is it more of a 'Lord of the Rings' feel, where there is magic, but it is much more rare and subtle, but because the PCs are participating in a grand epic, they end up having more of these 'rare' items (mithril mail, glowing swords, star glass, Elven cloaks, not to mention a magic ring) than would be expected in the setting? Or is it more of a Conan-esque world where any magic is corrupt and evil (possibly with a Great Old Ones vibe), life is cheap, but the wine and song are plentiful?