As soon as I stopped trying to get the purple orbs is when I got them all. Once you get to the fat pyramid structures spawning, the purples start spawning really quickly.
This game in no way simulates fishing. It seems like it was specifically designed with compulsive purchasers in mind. If you want to spend a bunch of cash to be "the best" at some weird fantasy fishing game that in no way comes close to the real experience... Why not buy a cheap fishing pole and go try the real thing?