Staff # depends on menu....how far you've prepped....how organized you are....how organized the hostess is....
Culinary students are hit or miss, I only use them for mega events where they shadow someone.
There are plenty of industry people who have chops and are out of work.
Since you are new to catering make sure to give yourself extra time.....time is essential.
Time to pack up and travel to event site, time to setup, time to chat with hostess....*tres important, time to organize your equipment/food/shtuff, time to get your staff on the same page, time to make sure the ovens are the right temp, time to......seriously time pre-party is essential, you DONOT want to start a dinner party in the weeds.
Staff, tell them what to wear (make sure to say ironed), tell them to bring knives or bartending equipment, tell them to be on time give them directions, tell them what you expect.....
Make sure to bring what you need equipment wise.