Why is my League of Legends client crashing and experiencing multiple bugs?

The League of Legends Client runs on Adobe Air, so the issue could be with that software. I would check for updates to Adobe Air. You can also try running the client in Windows 7 compatibility mode.

It is easy to blame the client as it does crash occasionally, but if it is repeatedly it has to be something on your computer. Typically you are missing some software updates. Try making sure windows 8 has all the updates as well as your video card. Even if you complain to Riot about it they will tell you, you need to upgrade your software. They are usually right.

League of legends has a new client that might fix your issues. The bugs are probably a result of adobe air like stated but this new client doesn't use adobe air!

I know this doesn't directly answer why you have bugs but hopefully it fixes the bugs all together :D