I don't know if this topic should be here but, I want to ask, How can I apply for translation campaign without any portfolio? or How can I get portfolios? thanks. 
I translated my first project as a co-translator for someone with experience. Another thing you can do is keep on trying without portfolio.. maybe it's not a top nodge proejct that will allow you to do your first translation, but you are building a portfolio that way which you can use later to translate in bigger and better projects. In translation bounties where you don't have to give up an example URL, I think many subscribers just lie about earlier projects and make a start in building portfolio that way.
Anyhow, if you do your first translation perfect... it will make it much easier to apply for the next one...