Tips for getting better with Lissandra?

I've been trying to get better with Lissandra lately, I like her alot as a champion and I got a free skin from rito for her last year for the whole good behavior thing, so I figured I ought to learn to play her, but I never seem to get any better than mediocre results with her. Generally I'm not sinking my team but I feel like my contributions are suboptimal. In lane she seems very dicey depending on matchups (I once ended up playing against an olaf with her in teambuilder shudder). I can freeze lane fine with her though (the ice puns) and in most cases she's pretty safe. Biggest issues are 1. Laning against hypercarries I can't seem to shit on them hard enough to prevent them from farming up a storm and 2. later on in the game it just seems like I can't do much besides some so so wave clear outside fights.

Items wise, depending on match up, I've been running flask into RoA vs more early game lane bullies, and Doran's Ring into Liandries or Morellonomicon for sustain farmers and hypercarries. Occassionally vs a heavy AD like Fio or Riven I'll rush Zhonyas.

Any of this I'm doing wrong or do I just need to up my mechanics?

thx in adv