Organizing a convention

Hello everyone !
two tattooists from a shop where I live and events organizers and myself are looking into setting a convention in my town, you know to return the favor to everyone who invited us, there was one which has been done here a few years ago, it kinda sucked, but people are still to this day asking if anything will come up eventually.
So we found a venue (with security), got a few meeting with the mayor which went well, we could even got sponsoship from the town and advertisement so on this side it's all good. However they are asking for our budget, plans etc ... And there's we in the blur a bit.
I ve attended many conventions but was always on the tattooist side of the events.
Basically what I'm asking, is there anyone who organized something like that from A to Z ? I ve got questions, such as, what to put in the booth a part of electricity, gloves tables/chairs and bio bins ? Did you set up a contract temporarily with the infectious wastes collectors etc ? Many thanks !