Mostly when you have them on you. Although some can interact with one another on a shelf or in storage too.So Canadia, when you say being careful cause some stones will cancel each other out, do you mean like if I'm wearing them? Or that they can't be near each other on like a shelf?
To replenish your crystals, either keep them in salt for a few days, or leave them outside for the sun and rain to cleanse. Careful with amethyst in the sun, they can fade.