tv ad slots are very expensive... and a full crew will cost many many thousands...
you may get away with using students, but if it looks amateur it may do more harm than good... we have all seen those shockingly bad ads for conservatories that look like theyve been knocked up in someones back room... would make most people thing twice about trusting them...
if you are determined, you will need a director, producer, camera op, clapper loader, lighting crew, gaffer, sparks, best boy, sound op and boom, editor, art director/props, makeup artist, wardrobe supervisor/designer, continuity/script supervisor...
possibly a composer and a DOP ...
some people here can often do more than one job.
for set you will either have to hire a studio or just find a location.
for a full shoot at a location you will likely need permission to film.
aside from crew wages, you will also have to pay for any equipment hire, lighting and camera van, generator, all consumables, provide lunch and refreshments, various expenses as well as travel expenses for a unit move if need be.
you may be best getting a radio ad made....much cheaper and easier
or get some one with animation skills to produce an ad that way so no crew etc needed.