I would start with 1 the first day, 2 the second and get to the 3 on the third day.
I sometimes take psyllium, in powder not capsule form. I tend to use it as an ' I dont want food, but I don't want to go to bed hungry', thing. Or, on a day when I have skimped on veg (sometimes life intrudes and its easier to eat a handful of cold meat, than sit down to a plate and 3 veg, followed by berries).
Because mine is in powder form, I pour a glass of water, stir in the psyllium, drink immediately, then pour another glass, sloosh the water round to catch the dregs and drink that too. Instant full feeling and excellent for the digestive tract.
If I was taking it in capsule form I would still have both glasses of water...