As you know the prices are higher now than earlier. If you want to spare the meals you should eat in the malls. There are so many types of cuisines like Italian (pizza, gyros), Indian (dahl), Turkish (dürüm, kebab), Hungarian (soups, fried chicken) style and so on.. These places are cheaper than in a regular restaurant however the city is full of fast foods places.
Near the Alle Mall, in the 11th district there is a local market (Fehérvári Road Market). It is open almost every day. You can find here local food, bakery, vegetables, jams, honey, flowers..
At the Westend Shopping center there is a roof bar and sometimes a local market here on Friday.
Behind the Corvin has a great food street with bars, restaurants, confectionery and there is an old movie theater, the Corvin mozi.
Budapest has 4 types of Metro line, and the 2 best lines are the yellow and green one. The point is both of them have the main stops in the city center (Deák square - Kálvin sqaure).
With the yellow one you can catch the Heroes Square between Deák Ferenc square. With the green one is good to go from the Kálvin square to the Alle mall (Újbuda központ, where is the Alle). If you want to stay downtown you won’t use it anyway. 🤡