I find myself isolating the best paying dragons and having one large habitat to their own, that way overnight I am maximizing my coin gain. When breeding I stick to the best odds with the fewest commons which have LONG wait times, so I do not breed the topaz often because of that horrible Sunrise which takes two days to finish (1 and 1).
I also agree with the red comment, I do not find value in housing red dragons, they are lousy payers in general and the habitats are not good for paying. I have been focusing on the pink hybrids because I can combine either diamond or pearl and the results are good.
I avoid the night-esque dragons because they do not pay unless you get an ultra rare and the wait times are quite long. For a period of time I was trying to breed night and diamond and I swear I was going for two weeks and it never rewarded me with the diamond hybrid I wanted, so I quit with that.
Winning the tournaments, winning the group events, getting the free dragons from the collection/album has also been a solid source of high quality dragons.
When I see neighbors who are not mining I do not get it, mining is free and you get great rewards for doing so..I think mining is a solid angle for this game.
For apples I maxed out the farms at 7 and have the Enchanted for all, which allows me the opportunity to do the 10 minute apples which based on price is the best return if you are around and watching. Overnight I either do the 5 hour apples or the 5 hour diamond dates depending on what I need. I also try to get what dragons I NEED to either make the most money or win on tournaments up to the level 8-9 area, while the less used or lower paying dragons I will keep at lower levels if they are not used for battles, they dont breed well or they do not pay very well.
I've never been able to get a Fairytale or been able to go down that breeding road, I have tried but no luck..same goes for the DINO or the royals or the cosmics. No luck trying different combinations and same goes for the tropic-esque dragons.