Ninja Gaiden Sigma

• The sword is pretty much the best weapon. You can play around with the others, but upgrading them really isn't worth it. The wooden sword however becomes ridiculously powerful when fully upgraded, but that should probably wait until after the normal sword is upgraded.

• There are a few spots that are really good for grinding money too, you'll probably realize em when you get to em, easy enemies that respawn and are right at the entrance to an area. No reason not to grind really.

• The normal sword is indeed the best weapon, you should also make sure you upgrade both the Dabilaharo (or however you spell it) and the Vigoorian Flails. The Dabi is the best weapon in the game against zombies, red dragons, and other fairly large enemy types, and the flails are the easiest way to deal with the particularly aggravating ghost fish enemies that show up in the last few stages.