So as you progrees farther in the game you will find yourself not only fighting more enmies but also stronger ones. The easiest way to fight, without fleeing like a coward, is to get the Hypnosis Plasmid and fully upgrade it. This is the most useful plasmid in my opinion, just find the strongest enemy and charge it up. Once released that enemy will fight for you. And at higher levels you can make Big Daddies fight with you too.
When you are in Ryan amusements look for a robot figure siting on a desk that resembles Andrew Ryan. Once you find the robot activate it. It will start talking. There should be some golf sticks there. Use the plasmid telekinesis to hit the robot in the head. The secret trophy is called nine irony. If you have played the first bioshock you should know why.
Once you get to the fishbowl go to diner. You have to enter through the back. In the storage room there will be two refrigerators. To the left of the refrigerators there will be two crates blocking the supplies. Trust me you will need all the help you can get once you take the shotgun.
When you start the game you need supplies. This submission will guide you to some money. In the first building that you are look for a bathroom. Go to the womens or dames bathroom. In the room there will be a locked stall you have to pay some money to open it but once the stall is open the will be some money.