Spells are fueled by the need for the outcome. Your intention is what causes the spell to succeed or fail.
You are the most powerful tool in your magickal cabinet. With just a thought the emotions and your pointer finger, you can cast the most powerful spell. Herbs, gemstones, oils, colors, etc can all help us to focus on what our intention is. Gemstones and herbs can add some energy to your spellwork, but really not enough to make a significant difference. By adding your intention to the gemstones, herbs, oils, etc, you're adding more energy to the spell and thereby increasing your chances for success.
Llewellyn's Complete Book of Correspondences is a fantastic book to have on hand for creating your own rituals and spells.