I have 12k IP, where should I spend it?

Rune pages (12.6K for 2)

That depends on what you like to play, how many runes you have, how many champions you have, etc. I bought all of the champions I like to play with runes for them and then I just started buying every champion from cheapest to most expensive to trade in draft mode. If you already have all the champions you like to play and runes for all of them I would suggest just buying every champion from the cheapest up like I am doing.

if you have every champ buy 3 random champ shards and keep them until the next champ gets released so you can reroll to save 2700 ip

Make sure you have all your runes and enough rune pages. Then you can add champions.

Save up for name change.

Assuming you don't own every champion If you own all 3150 or lower champions, I'd say buy Champion Tokens in sets of 3 to start getting some expensive champions for cheap They're 1700 IP