To determine the type of your Pokemon's Hidden Power, you take the Attack and Defense DVs and convert them to binary. For my Houndoom, that would be DVs of 1 and 8, so I'd use the numbers 0001 (1) and 1000 (8). In order to find the type, you use the last two digits of ...
Spend these on new Magic Items or upgrading Delicious Food (first) and Song of the Moon (second). You should have plenty of time to mop up the last of the Hidden Fish in these days, and make sure you keep unlocking Coral/new fish types and try to never get more than 1 of a...