What is worth buying in the daily shop?

I would appreciate if there's any community-made guides/tips about this, but I unfortunately can't find any.

Anyway, how do y'all choose/gauge the value of what you want to buy from the daily shop? For me, I'd like to prioritize dragons/items that can give me more resources, but I have trouble on what to spend my gems and coins on since I just started like a week ago lol. For example, are 100% epic items worth the gems or is it more worthwhile to save it on 50% to 100% discounted folklore and zodiac items? How about the boosts like gold boosts and the like?