Geting 7800IP champions for 5100IP
Im not sure how many people use this method to get champions after they have all champions, but i use it.
this method can be used for 6300 champions too but only if you have all champions but 6300IP champions.
So it works by buyng 3 "Hexteck Mystery Champion Shards" and each is 1700IP then you merge them into a random champion, http://image.prntscr.com/image/906e99282e7b4d33822526b0e5958300.png
i just got Xayah by doing that and you save 2700IP for runes :)
sry if this is a popular method but i just felt telling it