Remember that this is a hobby. Absolutes are for religion and politics.
You are trying to understand a complex ecology, and you need to start at the beginning. Learn about the nitrogen cycle, then about the parameters you want, and how to control them (pH ~7.0, dGH 3-5, ammonia/nitrites/nitrates ~0, Co2 planting appropriate, lighting planting appropriate, fertilization planting appropriate).
Understand your part, clean enough, but not too much, change water as close to weekly as is comfortable, feed your livestock appropriately (3-5 single bites per fish per feeding, inverts very lightly).
Your best mentor is a good book, so as not to get overwhelmed. (Aquarium plants is a good beginners book.)
Lastly be willing and able to make mistakes without having your brain explode, or else your brain will explode.
Good luck friend, and remember, have fun with it!