Heres my 100% Achievement Guide for this game and this could be (And i very much advise you to do this) your first achievement of the game you unlock.
There are Skills you can upgrade by using CP points gained after interacting with items through the game, completing levels etc.
Spot Hidden, Investigation, Occult, Strength, Medicine & Eloquence.
To get the majority of achievements through the game (Bar 3- 2 are endings)
My advice is you put your points into Spot Hidden basically straight away.
The reason for this is 1. Achievement unlocks and 2. We need it for the "John Legrasse" achievement later on in the game for finding 20 hidden objects.
Soon as you can, put everything into spot hidden and this unlocks straight away.
Go to 4:40 in playthrough 1 video to see where and when it unlocks!