Elongated torts are omnivores. So there is a huge variety that they can be fed.
Tort safe weeds, fruits and vegetables like squash, shredded carrots, berries etc. Mushrooms, worms, roaches, slugs, the occasional hard boiled egg even.
If you're still looking for food suggestions, I used a couple Herp articles, that I probably found links on this site, and looking at care sheets of different Elongata breeders. Personally, my tortoise won't eat any thin grasses or insects for whatever reason, so I stick to broadleaf lettuces, carrots, fruits, collard and turnip greens, a tiny bit of cat food or Zoomed box turtle diet, Maizuri large pellets, mushrooms, and other sundries on a schedule. They can basically eat everything, but if you want to be safe you can check the Tortoise Table website and exclude anything that is high in goitrogens (sp) or hallucinogenic.
-From MattJReptiles (http://mattjreptiles.com/)
"Natural grasses, true leaf lettuce, romaine lettuce, endive, escarole, red-tip leaf lettuce, tomato, small amounts of green beans, yellow squash, small amounts of soaked monkey biscuits and canned cat/dog food (once every four to six weeks), assorted soft fruits (ex. banana, melon, papaya), washed hibiscus leaves and flowers (no pesticides) and fresh cuttle bone."
-Another article. pgs 7 and 10 have diet observations. (https://www.zfmk.de/dateien/atoms/files/ihlow_et_al._2016_indotestudo_elongata.pdf )
"Captive I. elongata have been reported to accept a number of foods, including: fresh or dried greens (i.e., morning glory, dandelion, kale, collards, alfalfa, clover, plantain, chickweed), vegetables (i.e., bamboo shoots, tomatoes, mushrooms, pumpkin, cucumber, carrot), fruits (i.e., papaya, mango, banana, pitaya), animal matter (i.e., earthworms, snails, shrimp), and commercial tortoise pellets "