Should I do Kaniwani or wait until grammar?

Disclaimer: I don’t have speaking as a goal.

Speaking before getting to know grammar sounds like it would be an uphill struggle to me.

My recommendation would be to start learning grammar, then begin immersion, such as joining in with the Absolute Beginner Book Club here on the forums.

The more exposure you get to the words in different contexts, the easier it will become to recall those words. You’ll also get used to common sentence patterns and what words and phrases typically are used together.

From there you’ll still need to practice writing and speaking to get better at it. But I imagine it’ll become significantly easier over time as you read, listen to, and watch things in Japanese.