Kratom dosage is always a personal thing. I know new users who take upwards of 8 grams, and veteran users who take less than 3 grams. Everyone has their own personal set point for best effects.
Because of my background in opiate usage, I have to use relatively higher dosages than many others. The best dose for this purpose tends to be from 6-8 grams. Those who deal with chronic pain seem to have similar ideal dosages as well.
For more energetic effects, you’re definitely going to want to take a little bit less. For energetic effects, I suggest 2.5 to 5 grams. Some strains tend to get more sedating at around 5 grams, but some others truly start to shine, so it is best to mess around with it and see what is best.
These are my overall experiences with dosages, and I suggest always starting at a lower dosage if you are using a new strain, as you never know how it will affect you. Typically 2 – 7 grams is ideal, though at upwards of 6 grams, some negative qualities can occur in some, like nausea.