In particular this research on how much vocabulary you will need to read and converse. http://www.victoria.ac.nz/lals/about/staff/publications/paul...
For vocabulary I did the following.
1. Learn a few thousand words from scratchcards. (4000-9000 words is ideal, use a memory technique such as linkwords.)
2. Buy a kindle and install the foreign language dictionaries.
3. Start reading simplified books. (Not children's books, they have a surprisingly large vocabulary. i.e. a 6 year old has around 6000 words of his native language.)
4. After this start reading 'normal' books, i..e hunger games. You may have to fetch a few samples from amazon to find authors with a simple writing style.
When you get to step 4, the vocabulary acquisition becomes fun.
Forget the Bennie Lewis guy, his stuff is pay for bollocks.