Compared to the average meal elsewhere, Taiwan is a cheap city to fill up your stomach. This is minus the specialty foods, of course, if you're craving a hamburger, it will cost you about the same as back home. My favorite of these cheap options is the lunchbox. Sold at a million different venues, they offer plenty of variety and are very filling.
Of these shops, some of my favorites are completely vegetarian fair. They don't use any garlic or onions usually but the food is extremely flavorful. Some of my favorite things are hand-rolls made of mushroom, sprouts, peanuts, and cilantro. At these restaurants, you usually walk in, grab a plate or box and a pair of tongs, then make your way through the line taking items that appeal to you. At the end, you place your food on a scale and pay per weight. You can always ask for white or mixed rice.
I went a bit crazy this day, they brought my favorite rice out after I had already grabbed noodles. There's lots of green vegetables and fruit hiding under the rolls. The rice is very good, mixed with basil and other herbs, it reminds me a bit of the flavor in some risottos I've had. The total cost of this lunch was NT$150 (that's US$5, cheap!)
Other places offer a "set" rice, one choice of meat, and three choices of sides. There are still plenty of options, the availability changes often. Vegetables, sausages, tofu, noodles, fried mushrooms, and more are available for you side courses. While meats range from fried chicken, pork, and fish.
Noodles, vegetable patty, fried mushrooms, rice, fried chicken filet, AND since I frequent this shop near my job, this time they threw in a few extra pieces of tofu. Total cost for this feast you ask? NT$50 (that's about US$1.70.)
As you can see the lunchbox is the perfect option for a filling and diverse meal on a budget!