Liquid vs strips
Liquid kits are more accurate and cheaper per test. Strips are faster and easier for kids or beginners.
The API Freshwater Master Kit is the hobby default. Add a GH/KH test separately if you keep shrimp or are running CO₂.
Category guide
Test Kits for Planted Tanks
Without testing you don't know why something isn't working. With testing, problems announce themselves before fish start dying.
Decision guides