I got all the types of ammo for my first avi's cannon except explosive.. I felt like I WASTED my skills on ChainShot and GrapeShot, seen people using Thunderbolt and Fury, so I knew I wanted them..
The "best" ammo is the stuff the enemy ships spout out at you.. RoundShot, ChainShot, FireBrand, Thunderbolt, and Fury!!
I didnt waste any skills on my second avi on ChainShot, GrapeShot or Explosive.. I filled RoundShot, Firebrand, Thunderbolt, Fury, and RapidReload. The enemy ships SINK so well..
Well, now I have to work on my 3rd avi, since my other two have mastered Cannon, which is MY FAVORITE thing to do.. watch ships SINK!!!
