You do not have to register business as a limited company, but the main advantage of doing so is that if you project fails then you are not personally liable for the debts of the business, unless you did not tell your creditors that it was the company they were dealing with, or unless you gave personal guarantees to creditors. If you form a limited company the tax man will write to youi as if by magic!
Insurance is compulsory for employers, and highly recommended for most busiiness activities. Yoiu will need a bank account. a trading name which can be youir name if you wish, you will need to think about ordering stationary etc.
A circulation of 2000 seems tiny. You will presumably be using the services of a commercial printer, and will find that print runs of many times that do not cost much more, and the greater the circulation the more ads you can pull in, and the more you can charge for them.
Your local chamber of commerce may have a scheme whereby start up businesses can get some free advice.