I use plastic containers I got from takeout, which is why I don't really buy Tupperware anymore. The best thing about it is that it's light and transparent so it's easy to keep track of the leftovers. Also, it's microwaveable so I don't even really have to take them out of the containers to heat them up.
That is a valid option too lol, way more economic. Take away food has better and better containers, I don't know how they can sell meals stored there for the same price because those plastics really have quality, I use them as well.