The most you can assign to dex/str/int is 15. You don't need to max the remainder to be effective. In fact, you shouldn't up your speed (initial AP and AP recovered per turn) and perception (initial AP) unless you have the constitution (max AP you can hold) to support it.
You can max out (full 5) 3 talents in the game with some points left over for flavour (assuming max level 20).
