A silly idea thought up.
Magical focus gems that produces magical clothes that goes by how much percentage it contacts the body. The more it contacts, the more efficient the gem is, and the more powerful the gem, the more covers the body. You’re basically wearing your mana
Colours of the gems amplify personal mana colours. So if you’re Yellow, Yellow gems would amplify your own, as well as Red and Green gems together. White gems would be usable with all, but can easily be tainted to a major colour, and black gem would be absorbent of other colours. To use whites, you’d either have to go all white, or balance it out with all the other colours, Which would mean less surface area for each gem to be efficient.
The Clothes in turn are an indicator of it’s mana. The more mana the gem has, the more it covers, and vice versa. So using up spells would burn up the mana and cover less.
The cutting of the gem makes it more efficient at focusing magic, at the cost of mana storage. So a raw focus can have a high storage, but makes spells unstable.