Toxicity is something you will sadly encounter in almost all online games. Put them on ignore if they're not giving constructive help, or are just being rude. Don't respond to someone being toxic, it just makes the whole team morale go down.
PvP is very difficult, you have a lot to learn in this game. Not only how to play and build champions, but how to counter and build against champions. So dont be discouraged, you can and will lose your lane, and games. Just try to figure out what you could've done different to help you and your team win. The thing you can do if you're losing a game is to ward. Wards are extremely important to winning the game. The support will usually (save for some junglers) be the only role that will build a sightstone. But, every role can help with warding. Just buying "green" ward every once or twice you back and placing them will help a lot.
For runes, I'd set up a basic rune page that can be used by most AD champions (One for AP as well) that are useful for the majority of AD users until you get the IP to make champion-speific rune pages. Something like AD reds, Armor yellows, Magic Resist blues, and AD quints.
ADC's is a botlane position usually filled by champions labeled as "Marksman". You can play fighters and others in the ADC position, but the meta (commonly played champions) are marksman that fill that position in most cases. They're the role responsible for doing a lot of damage late game, by building damage items instead of tanky items. So they hit very hard, but are squishy. You generally want to try to keep them alive in teamfights if you're playing someone with Crowd Control (stuns, roots, fears, etc.). Or go for their ADC if you're playing a champion with a lot of damage. But don't go and run in 1v5 to try to kill them. Go for them if they're open or caught out, with keeping in mind you still dont want to die.
As for summoners, the reason you see Flash a lot is becuase it's considered by most the strongest summoner spell. It's basically a get-out-of-jail-free card when you being ganked (another lane comes to yours to try and get a kill on you) or when you're stuck in a situation (flashing over a wall to avoid dieing). Or flash can be used aggressively, by flashing forward, flashing over a wall, ect. to get a kill on an enemy.
If you need help or have questions, feel free to add me in-game. Im not high ranked or anything, but i can help with basic things.
