NegiSpongie

I was also thinking Pizza Delivery

Either Pizza Delivery, Help Wanted, or Band Geeks.

Pizza Delivery because it’s a very early episode if the season, is great and well-loved, and a classic. Other good options would be Help Wanted (due to being the pilot) and Ripped Pants (same as Pizza Delivery but to a lesser extent since it’s not as good)

I actually would say Band Geeks shouldn’t be the first episode, because part of the reason why it’s loved is squidward winning for once, and that wouldn’t effect a first viewer, who hasn’t seen much of Squidward, as much.