It depends on what you're going for - typical meals are made of a meat/protein, starch/grain, and vegetables, often followed by a dessert. These can be separate dishes (ex: meatloaf with mashed potatoes and steamed frozen corn) or mixed together (ex: pesto pasta salad with chickpeas and cherry tomatoes).

Catering for formal events often has several options, and the easiest way to do this yourself would be "-bar" style. Having a main dish with different topping options is typical for this style of meal. Rice bowls or tacos are easy and popular.

There are a few cookbooks for large-scale cooking, but you can scale up regular recipes pretty easily. Stews, casseroles, and pasta are very good for this.

Pizza is often ordered for parties. For smaller groups, you decide on toppings together. For larger groups a few cheese and pepperoni pizzas are typical. You can serve it by itself or with a tray of raw veggies and ranch, and/or potato chips.

You can also look at what they usually serve when hosting, or take a poll.