Leticia, I don´t advise you to learn X words a day, I agree with Charles when he points that out.
What I meant is, English has a "core" of words, one can take that list and strike out the words that he/she knows and little by little to search the others, not necessarily in order.
For example, someone interested in car and motorbike engines would meet the words "piston", "cylinder", "engine configurations" and the like.http://animagraffs.com/how-a-car-engine-works/
One into fashion, "gossip", fond of knowing how celebrities live, etc, would go to a magazine like People
and would soon be familiar with words like "scoop", "preview", "looks" etc.
Whereas the techy-savvy would to Wired magazine
, the ones interested in the UK would read BBC (the beebee site) etc...and the newbie one could go straight to the Flatmates (still within the BBC site). Many would go to The Economist or Forbes, to know about finance and the state of the economy in the world (but not only that, one can find Science and other things there.)
I think doing something you like will be productive to your learning, then you can make use of a list to strike out words, to remind of some etc.
Indeed, context is always a powerful tool, and as I stated before, with time you don´t even count how words you know.
Or you do, but in the range of thousands, he hee. With the help of a site like this one (there you can set for English or Portuguese, as you wish):http://testyourvocab.com/br/http://www.lingholic.com/how-many-words ... ize-a-day/
Again, I didn´t mean one has to memorize tons of words, but one may (or may not) use a list as a reminding tool, to scrape the words one knows or even to see words in a new way (the several definitions, with the aid of the "word in a sentence" etc...