I also have this problem.. normal i have around 18 ping and thats great.. now i play with 100+ ping going up to 260... especially when the minions come and start to fight my ping goes up like no tomoorow also after a while it goes back to around 30 and it keeps going up and down! 30-260 after a couple sec back to 214... its incredible i have 2 modems at my home. my external modem has the most issues with it makes it unplayable, the main modem has the same issues but thats a ping from 30- 140 but still unplayable in my case.
also after resetting both modems like a million times i get some better performance but it still occurs so i wont play any ranked soon! until it gets fixed.. also nemesis will be there without me.. makes impossible to play a normal game with just around 140 ping!
riot please fix this its around 3/4 days now.. lets say somewhere around 11-2-2015 / 12-2-2015 i think its something with the 5.3 patch... but untill its fixed no league for me

makes a allround fill player sad :(