(Some people seem to get lost later on in the game if they go by a 2 DEX and 1 STR basis. Since they forget what to invest into next. So here is a simple solution.)
Your DEX should always be double the amount of your STR, and your SPR should be 1/4 the amount of your STR.
An example would be if you had 200 DEX, you should have 100 STR and your SPR would be around 25.