After you’ve ended the first level, you’ll be awarded points based on your performance. The higher your performance the more points you’ll receive. If memory serves me 180 for Easy, 250 for Normal and 350 for Hard. After ending the first level on normal the first time, use your points to purchase the Rifle Gun Rod form, the Raven’s Panic magic, and the Element Shot magic. If you don’t have enough points to purchase them all focus on the Rifle and Element Shot. Now proceed to start the 2nd level. Once the cut scene ends select “Retire” from the menu and return to the main menu. Be sure your game saves.
Once back out at the main menu select to start a new game. All your stats from the previous game will still be in effect. Armed with the detailed guide above for the first level go and wipe out all enemies including the second Tank and all enemies you avoided before. Redo this level a few more times on the Normal difficulty to build up your Element Shot, Ravens Panic, Main Gun, and Rifle Form. Once you have each of those at, at least level two continue repeating this level on the hard difficulty.
Now you’ll be getting 350 points each time you end the level. It usually takes about 10-15 minutes to complete the level. You’ll need to do this for about 5 hours to max out all weapons but that’s really not needed since you have to play the game anyway. What I’d suggest is that you purchase all Gun Forms, and Magic. Get your Magic, Health, Main Gun, Rifle, Element Shot, Ravens Panic, and Willpower to Max then head out to play the game on Easy. While playing the game on easy use the points earned to Max out your Gatling Gun, and Ancient Wall.
This achievement will unlock once you’ve upgraded your Health, Magic, and All Gun Rods, and Magic Abilities to level 3.