Ping issues: I need some help

When i first started to play League, I ran at around 83-90 ping. But only recently has it jumped to around 200-450. I've looked up a few things to do such as use a eather net cable, and close off other programs, and even set league of legends to high priority. Now at first it seemed to work for a few games, but now its jumped up to about 350 ping. Does anyone have any tips about bringing it down.. (And no, buying a greater internet plan is out of the option)