MySQL Database going round in circle

I keep redesigning this DB from the ground up with no luck of a stable design plan

the site is http://advertisementworld.com/ and belive it or not is done in all HTML wit habout 30 folders and subfolders govorning sections.

im trying to come up with a good design document outlining what kind of database needs to do but the best im comming up with is

"Client creats account and can add new adds, ad reginster stanrt and expiry date and deactivate any adds past expiry for manual deletion or reactivation by admins.
no cron tabs, checks will be dine when any page acessing the DB is loaded ie "if date > expirey date set status = inactive"

i know i need at least 2 tables, one for clients, and one for the ads, the add themselves come in several sizes and page side i'll design dispay but could use more help coming up with a idea for design ie fields, additional tables...

i want to keep the site the same as it is now just easier to manange