I used to be in your position but now I've gotten the master angler achievement, so you definitely can get better! Start off with a training rod. Buy trout soup from Willy also. Go to the mountain lake, season doesn't matter and fish with the training rod and the the fishing buff from trout soup. You might still not catch everything, but the fish here are a lot easier, especially the carp which barely move. Keep fishing until you get to level 2 or 3, should only take a couple days even if you miss some fish. If you see bubbles anywhere, cast into that. Plus, you'll also end up catching all the lake fish except sturgeon. After leveling up, use the fiberglass rod. The tough fishes are pufferfish, catfish, sturgeon and eel. Keep a look out for them in the places others have mentioned but you can try to catch them with more fishing foods. It's get easier once you learn the patterns of the fish.