I really like the 300-500 word method. Before I threw in the towel on learning Spanish (mostly because I lost interest), I was using flash cards with the base words from this site: https://fluent-forever.com/the-method/vocabulary/base-vocabulary-list/#.VBChxS5dVhT

Of course, learning proper tenses and immersing myself in the language more through music, tv, and travel would have helped increase speed, but that is the best first step