Visions are not quite physical. They have to do with your perception, and there is no spell to just make you poof and 'get it'. Developing psychic sight takes practice. I would suggest trying ESP cards: Get like 60 flash cards and make up 5 simple symbols. Make 12 cards of each symbol and practice guessing which symbol is on the cards.
If you are already a 'master' of such magicks you probably need no aid in meditation. Take up using tarot cards and as you read for people add in your intuition about the situation.
Stones like Lapis Lazuli (and just about anything blue) is good for helping to strengthen and open the 3rd eye, but all of your chakras have to be functioning properly to get a whole lot of benefit out of it. Visions are presented through both the crown AND the brow chakra, so take that into consideration.