In order to increase your vocabulary try memrise.com, it is an efective instrument to learn new words. To achieve a better use of the new words, you can prepare some compositions and post them on Italky, maybe somebody will correct them!

Learn vocabulary words from a list of commonly used words or from modern literature/newspapers, then try using the vocabulary yourself through italki or Skype and see if people don't correct you.

When you learn a new vocabulary then you should use it everyday by talk with people . It will remember. I'm also learning english and chinese. Can we be friend to make our language better. Feel free to send message.