What to choose in the beginning
At the very beginning of the game, you will have to choose between the Sword, Staff or Shield as your power of choice and give up another one in return.
If you're looking for more Strength, low Defense and medium Item stock; then go for the Sword and leave the Shield to start with 3 AP with less Defense, or leave the Staff to start with 1 AP with more Defense.
If you want more Defense, medium strength and high Item stock; go for the Shield and leave the Sword for lower strength but with 3 AP, or leave the Staff for more strength but 1 AP.
If you want more MP towards the beginning and ending of the game but low item stock, choose the Staff. If you leave the sword, you'll have a very balanced status, but if you leave the shield, you'll start out with low defense.