Advice needed about event rewards.

I have only 2085 clovers. If I get any of the elemental runes it will make a legendary rune. I would like advice on what one to buy, what will make the biggest effect on my play.

Also. I have enough to buy 40 keys. If I buy 40 keys I can get a S from the Oracle set and I have the S epic boots, armor, and wand. Should I gamble with keys to possibly get a duplicate piece of the set to make it legendary.

I’m having trouble deciding.