Specifically looking for recipes that are relatively cheap, filling, and aren’t too time-consuming so I can keep up a routine without getting burned out. I have a 10 cup rice cooker so rice combined with other things would be pretty easy. I have a Costco membership and there’s a restaurant supply store near me, as well.
If you can get your hands on big pots and can bake, a soup with bread might work too.
Lentil & vegetable soup is delicious, filling and can be made to any flavour profile. Root vegetables and tinned tomatoes work great in it and are cheap. I tend to blend it with a stick blender and it’s very nice. And if you can bake bread loaves, you don’t need that many for 50 people as a side.
A lentil or a chickpea curry could also work with the rice, if you make a huge pot, it would be a filling meal for lots of people. The sides like raita is also something that is easy to make in bulk.
I have also made vegetarian lasagna and other casseroles like that for pretty big groups and it works great. So do salads. I have a go-to “chicken” & macaroni salad that I make pretty often. The chicken is soy strips, the cheap dry kind.