Hi, floor standing tickets all cost the same. I don't know the price for Portugal (maybe someone else can say how much it was), but in other European countries they were between 90-115 EUR. Ticketmaster has a very bad habit of increasing the prices of leftover tickets, so that if you buy now, they might try to charge you several hundred Euros for a floor ticket which is THE SAME TICKET TYPE that usually costs 90-115. So please don't buy that, you will NOT get any better view or any advantage.
I'd recommend you to wait until closer to the show and buy a floor ticket from another fan who can't go at face value. Close to the date, there will be many such opportunities. As for the view, it depends on how long you are willing to queue. Many fans start queuing very early (7 or 8am) to get close to the stage. It's simple, those who manage to get in early can choose their standing spot.
There is one additional ticket category called Early Entry, it's priced around 230-260 EUR and allows you to be part of a group of ca. 1000 people in a separate queue who get to enter ther stadium before everyone with normal tickets. You have to queue early for this too to get a good spot, but it kind of guarantees you to get barrier.