Spaced repetition systems (SRS) are an efficient way to memorise large amounts of vocabulary. Sometimes rote learning is the best way to do a certain task, but SRS apps can help you do it the smart way.
A popular and user-friendly option is Memrise. It’s free with ads or you could pay for a Premium account. It has a fun interface which feels very gamelike. If you’re studying for the TOEFL, here’s an example of a Memrise deck made by me:
My personal favourite is Anki, which allows for greater customization but has a steeper learning curve. I used it to study for the Japanese Language Proficiency Test (JLPT) and the Kanji Kentei.
Both are free, so the best thing to do is try them both out and see which one you like!