STILL! Still can't set up another email for iMessage/FaceTime!

Question

*Yes. I will repost this discusion if it is sent to the second page with no reply or is replied to with an incorrect response.
I already have two iPhones and an iPod touch, and a Mac set up on my iTunes account. The iPod and Mac each have their own gmail account they use to recieve iMessages (one of them is my Apple ID). The two iPhones each have their own phone number they recieve iMessages from. I now want to set up an iPad on that same iTunes account with iMessage with a third gmail adress to use. When I try to set up iMessage, I am shown the two gmails and phone numbers from my other devices but no option to add another email like all the tutorials say. Is there a limit of 2 emails or something? There is no way I am making a new Apple ID just for iMessage. I tried to look for the option in Messages and Settings. Please tell me if there is a way I can add a third email.
No, there is no "Add account..." button like in the screenshot walkthroughs. Is there some kind of limit? Why won't it let me add another email?
10 points go to the first plausible answer!

Answer 1

You asked 3 or 4 times.  
You say you already set up the gmail account App, so you must have added this gmail already???  If you didn't you could not get mail in the App.
When you set up iMessage on the iPad, it must be set up with the unique gmail address.  There is no limit to email addresses.  I have 4 on mine in iMessage, all unique, one is my iCloud.