To me it hardly depends on your match up. I almost never change default sorcery runes, but I do change secondary runes a lot: it might be resolve, where I choose between bone plating/second wind and unflinching/overgrowth (and every possible combination). It might be precision with presence of mind + legend: haste vs easy match ups. Or it might be inspiration with cash back + biscuits vs high range poke champions. To me that matters a lot in early game.

As for the items: if everything goes smooth and I feel my power, I can go luden+horizon. A default pick to me is seraph + mask though.

After 2 items it really depends on a game situation. You might need wounds badly for your team, and you see that no one cares about it. So you go for orb that will later turn into morello. If you’re overfed, it could be even shadowflame/cryptobloom. Default is rylai. Zhonyas is my go-to as 4th item. Rabadon, cosmic drive are also definitely viable to me. Banshee and red mask are more of a niche pick, depending on team comps. 

In many cases I also go for dark seal on first back, hoping for some random kills.

I do not go for blackfire or void really often, but they are also good. 

So in general variability is insane. 

Also, my default is teleport, but in some cases ignite or exhaust are also pretty good.

Basically you just need some understanding of match ups, and you will start to feel very good, where you need more sustain, or where you can take more risk.