I sort of wish they sold energy boosters instead of packs or the content-skipping runes. Alas, the only real way to get more energy is to be lucky with Duties.
As far as the fish scarcity goes - try feeding 1* fodder to preferably level 1-5 dragons. Yes, it goes to waste, but you might not have to buy storage expansions(spend over 1k runes on that). I only feed 2*+ to my main team, otherwise it’s not worth it.
Finally, as far as I understand - Breedery is just pure random. I’ve merged 3*+3* of various types for days almost on cooldown, always having fish at the ready - and the best I got was one 3* hybrid and some basic 3*-s. There was a day when I got like 5 2* Nadders IN A ROW.
I still have an itching suspicion that dragon training level affects the odds, even though a person said that support told him otherwise, but I don’t quite have the testing material.
Imagine that the game is a grindwheel that you have to spin. I do only farming quests and avoid even the rune quests, only doing the scale quests when I have a Duty specifically for a quest and not the story level.
So one such quest gives you, and I assume you are doing Barrens - 1400g, 3000 fish and ~7 eggs. Which means that you still need at least 2 runs to hatch a single egg, but chances are that you’ll still get spare gold from it. That means that from 2 runs and 6000 fish you’ll get only one dragon hatched. Sure, from 3 runs you could get 2 hatches, but the point is that from this basic ratio you get more fish than you’d spend on training, unless you really train some high level dragons.
I also am ignoring\rerolling leveling\training quests, unless it’s ~6 and the reward is 5 energy(the best possible reward), because then it still helps to spin the grindwheel.
All of that should keep you stocked with fish for breeding, and remember, it’s 2k fish per hour, you should never NOT breed and I would not recommend to spend any fish if there is a chance of a 1* dragon. Every hour you regenerate 6 energy, that’s technically enough, if you don’t overspend Fish to level dragons and you get some random Duty extra rewards.
Of course, there are always Big Chests, their rewards every couple of days is also handy.
Finally, there’s a dedicated thread for that, where people discussed feeding 10 dragons at a time. The idea is that you save fish, because EVERY level of a dragon gives ~50fish increase per piece fed. It starts at 1500 for 1* training and goes up to 3000 by the time you reach 30. 2* training starts at 2000, so that’s even more painful.
So if you feed a level 1 dragon 10 pieces at once even if he gets 15 levels or so - it will still initially be 1500 per piece. Tricky to do without large storage, but it saves some thousands of fish.
However, as chances are that you’ll have 75% of 1* dragons and only 25% of 2*+ - even feeding 1* dragons to anything above level 10 would drain all your fish. So, since there is no way to sell\convert dragons to resources… which is probably an idea worth suggesting - you just dump 10 1s for 15k fish to some 2 dragon that you are later going to use for feeding(you’ll get a tiny bonus), and you free up the storage space for more.