There are so many different crystals that you could use to aid in manifestation, depending on what it is you want to draw into your life. If you're looking to bring more love into your life, use Rose Quartz. If you are manifesting a pay rise or better job choose Citrine. If you're looking to manifest a sense of calm and tranquility in your space then Amethyst is your best bet.
Generally speaking, my favourite all rounder crystal for manifestation is Malachite. Malachite is the stone of transformation, enabling you to connect to your yourself and see exactly what it is that you need to draw into your life. It will rid your surroundings of any lingering negative energy, cleansing your space and allowing your desires to manifest themselves into your life in a clean energetic atmosphere.
To achieve a sense of clarity, I'd suggest wearing an Amazonite bracelet. Amazonite is a very calming stone and helps to connect you to your intuition, filtering out information that can make the brain feel foggy. This crystal helps you to see more than one perspective and reach a higher level of consciousness. If you're faced with a dilemma or want a bit of guidance on a situation, I would always recommend Amazonite for the mental clarity that it brings.
Finally, one of my all time favourite crystals, Citrine. Citrine is the number one crystal for making you feel positive and happy. it holds within it the energy of the sun and is incredible for lifting your mood. It's also a great crystal to inspire creativity and draw in abundance. I have one on my desk at work to keep me feeling inspired but also in the wealth corner of my home.
In Feng Shui, the wealth corner (associated with prosperity and abundance) is the far left corner from the main entrance door of your home. Placing citrine here encourages a flow of positive energy. Think of a piece of Citrine like a ball of sunlight in your home that never dims.