I would wait to add another language until you have a decent foundation in one. That way, you won't get confused. For if you start several languages in the beginning, it will probably confuse you.

Learning Spanish, Italian and Portuguese would probably be a disaster :P

I found that the 2nd language that I learned that had similar roots was confusing at first. I learned Spanish then French, but after that, I learned Italian and Portuguese and my brain adjusted. Now they all reinforce each other and I can recognize patterns to predict words and meaning.

Confusion may happened if they share the same roots.

I reckon it's easier to practice German / Portuguese at the same time than Spanish / Portuguese for example.

Depends entirely on the person. At school I studied three languages (two with similar roots) at the same time and had no problem while my brother struggled with one. Here I'm doing two and again no problem. I'd give it a go. You've nothing to lose.

Oh yes.

I think I'm going to try Spanish and French together for the next month. I'll report back!