There are two very important types of fluency or memorization that should happen in elementary school.
1. Learn your time tables - I recommend Time4MathFacts as Gamified and Effective. See this math facts educational article
2. Retain your vocabulary. While learning vocabulary has a number of clever techniques, there's a different question of how to retain. Research says that for most of us, 12-15 touches with a word, different contexts, different ways over 3-5 weeks provides a very high probability of long term retention. Read about vocabulary retention.