Just launched my first Android app — how would you market it from zero?

I've just launched my first Android app on Google Play and I'm trying to figure out the marketing side.

The app is called When. It helps people keep track of date-based things they usually forget — warranties, subscriptions, expiry dates, documents, receipts, borrowed items, birthdays and other reminders.

The product is live and working. My problem now is distribution.

I have very little experience with app marketing, so I'm trying to build an actual strategy instead of randomly posting links everywhere.

If you were starting from zero today, how would you approach the first 100 users?

I'd especially like advice on:

1. ASO — what should I optimize first?
2. Organic content — which platforms are actually worth the effort?
3. Reddit/community marketing — how do you participate without becoming spammy?
4. Influencer/creator marketing — is it worth trying this early?
5. Paid ads — when would you start spending money?

If you've launched a mobile app yourself, I'd really appreciate hearing what worked, what didn't, and what you would do differently.

I'm here to learn, not sell anything.