Jungle tips from a jungle main:
Armor runes are fine, I'm actually using a 15 armor rune page on champions right now that I'm not used to - as I get more used to them I can lower to the standard 9 armor (yellows) - but virtually every jungler uses at least 9 armor runes (yellows). One of my jungle rune pages for this season is 29% attack speed + 15 armor - makes early clears very fast and enough sustain to gank on many junglers (AS everything except yellow+blue armor). Works well for Devourer champions and/or Diana.
A lot can be done to improve your jungle clear, watch some videos - especcially of high level champions playing your preferred jungler - the difference between a high level jungler clear and a novice at that champion can be night and day - typically they can full clear without backing with every champion - often throwing a gank in there somewhere too.
Wards. Good ward placement is essential as a jungler, you need to know wards just as well as a Support main - because you need to anticipate what is warded - and then either go around or sweep it when you gank.
It's your job to watch the placement of every member of the enemy team - but particularly anticipate the enemy junglers movement. You should warn of where you think they will gank next, or go to there and prep a counter-gank - or at least a deny. If mid leaves mid lane, its your job to warn bot or top as much as it is mid's job - being a jungler is about a lot more than just PvE'ing NPCs to death: you are the fulcrum of map control (and objectives), you are the basis for ganks, and you are responsible for anticipating enemy ganks.
Lastly - vision and awareness. Having good wards and scuttles and wolves and vision of the jungles is only helpful if you are staring at the minimap all game - if someone peeks their head into vision for a second, you need to take notice of it. Having vision is meaningless if you don't notice what the minimap shows - so some people get good at warding, but still struggle to make the right calls: often the difference is they didn't see what they were shown.
Get comfortable enough and fast enough to clear your jungle without looking at your champion - spend your time watching lanes. Stare at the minimap. And click your thoughts.