DEX is the most commonly used stat. DEX affects initiative and armor class. It is common for characters to perform DEX checks and saving throws in various scenarios. However, Each class has a stat that is best for them. If you are playing a martial class, try max STR or CON. However, a Druid planning to take Wild Shape would not need high STR or CON. Druids take on the CON, STR, and DEX of their selected beast. WIS is much more critical for a Druid.