I'm learning Russian in my spare time, and have used the goldlist method to build vocabulary. The goldlist method is great, because
1) There's no cramming. Nothing is worse than cramming, and
2) you can have breaks as long as you want.
I reached 2200 words the first year, while having many week long breaks. I kinda stopped the regular vocabulary building around 2014, but even after months of inactivity, I can easily pick up the goldlist and continue where I stopped.