There are plenty of different ways to grow your vocabulary right away, including:
Flashcards
Use a flashcard app and take your words with your wherever you go. Practice them in your spare time.
Create categories
A great way I've found with many English learners is to find synonyms to some words and create categories. For example, you can put the most common words you need, for example, for Food, Travelling, Personality, etc. Then, write words you know well and put them at the beginning of a list. After that, you can put five other words underneath it with similar meanings. For example, leave – forsake – abandon – quit – give up. This is bound to grow your vocabulary!
Reading
Read widely (and slowly) and take notes alongside whatever you're reading. For example, if you're reading a book in English, make a mess of it! Use a pencil to underline, circle, and add definitions of words you don't know. Look them up and add them to your flashcard app. Here's a great list of classic English stories [link deleted by moderator] where you can find a book to suit your level.
Conversation, conversation, conversation
Nothing beats conversation to grow your vocabulary. If you have a tutor, language exchange partner, or willing friend, you can get corrections while you speak and also, you'll start to pick up word you want to say but don't know yet. Then, you can look them up and add them to a flashcard app.