How should I test my project correctly?

Hi there, I have a question.
What is better - manual testing or automation or both of it is necessary? I started manual testing of my new project not so long ago. If I’ll need automation testing - when should I start it?
What is better - manual testing or automation or both of it is necessary? I started manual testing of my new project not so long ago. If I’ll need automation testing - when should I start it?