Hello and WELCOME. The web site called thetortoisetable.org has a lot of edible plants to look up. You can look there. Also most people feed Mazuri tortoise food, soaked in water to make it soft. Also a mixture of dark leafy greens, kale, endive, mustard greens, spring mix, dandelion etc. Prickly pear cactus and some times the fruit of prickly pear cactus. A varied diet is important, so don't feed just one or two things, mix it up. This should get you started, others will be on soon to give you more ideas.
If you have a hatchling, read the threads at the bottom of my post. They are all really good for a healthy, smooth sulcata.