It really depends on what your goals with fasting are. If it’s weight loss, no need to hop right in to long fasts, alternate day fasting for example gets terrific results.
What also helps me is getting on a keto diet before starting a fast. If you’re already in dietary ketosis at the beginning of your fast, you skip that first 48 hour brain fog and general unease (keto flu) as your body transitions from glucose-stuffed into fasted mode. I also find it helps my hunger starting in keto.