Since you have Chakra, I recommend using that in most of your breedings to maximize your chances of getting a hybrid.
When you are trying for something specific, try to always have 4 types in the breeding pool. Remember, minor types are your friends here. For example, if you were trying to breed the Gorgeous Dragon, I would recommend using a Black type since it splits into Blue and Purple (Gorgeous's types). Preferably it'd be a Black and Blue or Black and Purple type, (such as the Midnight Dragon or the Illusion Dragon). Then breed it with an Olympus hybrid of the type you didn't use (Blue or Purple) since there are very few Olympus types and it wouldn't add much to the outcomes. Thus you would have four types in the breeding pool, Black, Blue, Purple, and Olympus, and you'd have both Gorgeous and Diamond in the outcomes, while keeping as little outcomes as possible.
e.g. Blackhole Dragon (Black and Purple type) x Nyx Dragon (Olympus and Blue type)
Alternatively, when you aren't trying for anything specific, I'd recommend breeding Wizard Dragon and a Green/Yellow hybrid, as that adds both the Diamond and Infinity dragons (for some reason) to the outcomes.
Finally, I'd recommend buying the Diamond Temple when it goes on sale. This is how I bred my first Diamond.