Simple:
1. Level your Stats. In the Long Run, always boost your stats instead ofHP/MP.
2. Stick to a "Role". A Hero who concentrate on one or two stats will pass more stats check and is more succefull in battle than "Jack-of-all-Trade". A Role can be something like "Warrior" ( STR + END) or "Rogue" (AGI + STR) or "Bard" (CHA+END+INT) or "Warlock" (INT+END) whatever you want your Hero to be.
3. If you are still unsure: END is more or less the most reliable stat atm. It Boost your DEF, HP and even your "healing spell", keeping you alive. Trinket and item that increase your DEF or END are kinda the best items in the game.