Depend on your trading style and the current price and potential of the token you want buy, every time can be a good time to buy. But first, you have to decide what is it you want to do first. Then buy or wait for a better price.
Most of the times people really dont know what they actually want to do. They are unaware of their goals and objectives and thus they cant be successful at any stage of their lives. Better to make sure you goals and tasks that you must achieve. You must know your timeline and your steps must follow that time sheet too. Dont get distracted with materialistic of this world.