Some teachers say there should be no rules. Some say there should be 100. The conventional thinking is probably no more than ten.
The number of rules you have doesn't matter. What works for one teacher may not work for another teacher. The same goes for the consequences you use as well.
The key is to figure out how you want to run your classes and take it from there. If there are only two things that you want to enforce, then have two. If you have 70 or more things that you want to enforce (like me), then go big. It doesn't matter.
Find what works for you. Don't have rules that you don't really care about enforcing. The key to rules is being clear and being able to explain why you have them. Once you do that, the number is up to you.
And please don't give me your dramatic reasoning that kids just won't be able to handle a lot of rules. Boo hoo. The world is full of rules. Better that kids get used to dealing with them. Your students won't hate you unless you are a jerk about it. Toughen up.