Strength is all about your damage, the higher your strength the higher you hit. This skill doesnt go up in stages and the damage add is also all about the weapon you got on.
Defence is all about Armour Class, its not a very usefull stat , seeing as it add 1 attribute every 5 stats. Armours/Shields/Helmets/Gloves/Boots help better. So you could put your defence somewhere else. (Note: If you arn't rich enough for some defence items to put on other items that need defence, you might still wanne put defence till 55)
Constitution is all about HP Regen and Energy Regen. Every 70 constitution it regens faster, its great for a berserking character, but you might wanne add it at higher level, because youll need your strength and stamina at lower level.
Intelligence is all about you MP. 1 Intelligence equals 1 MP. Mages always do 1 intelligence for every 4 magic.
Stamina is all about your HP. 1 Stamina equals 1 HP. Warriors should do 1 stamina every 3 strength
Magic is all about you MP Regen. Every 40 magic it regens faster. High magic is great for mages. You should try to keep up with 1 intelligence for every 4 magic you add.