Brand new to LoL

Sometimes you have to be willing to die for your team. Either so you can win team fights or for towers/inhibs. It's hard to say when it's worth it, but sometimes it is.

Oh and if you play a tanky support, you will be dying to protect your carry. A lot

Okay. You died for your team, which resulted in the rest of your team killing the rest of theirs, which means their team came out with a disadvantage, which means that you won the fight. I didn't mean to give a cookie cutter example, just an example.

You can't rely on on your own lane not snowballing. That'll win like what, 50% of your games. Which means you'll stay at the same elo.

You have to have the mindset that "I know this matchup and I know that I will win this matchup. And then I'll gank other lanes and make sure my own lanes snowball too, so we're practically guaranteed to win."

But don't worry about that now. Just worry about not dying, lolol.

That doesn't make what I said wrong. With my laning example, you're not relying on anything--to use more general terms, your goal is to play the lane correctly, to give your opponent as little advantage as possible over you, if any at all. If you are in a matchup that you can't not lose, then you play in a way that cuts your losses and makes you productive elsewhere, as opposed to trying to win the lane in the same matchup; you'll probably end up feeding if you do this.

Either way, I was giving examples to make the idea more concrete. The philosophy of making sure the enemy doesn't win applies to literally everything you or your team does. Teams level 1 invade Amumu because he won't be able to do much for some time without his blue. You don't trade with a Draven in lane because he will outtrade you and end up killing you in 45 seconds. You take Dragon after a successful fight at bottom because, first of all, it's probably free gold, but if you don't it opens up the possibility of the enemy taking it some time in the future. You gank lanes for several reasons: It can deny the enemy laner an escape, it can deny them gold and exp if you kill them, and at the very least it makes someone spend money on wards for safety.

Winning is often a result of the enemy not winning. When you have taken away an opponent's advantage, you've established one of your own. If you play so that the enemy doesn't win, you're still working towards the same result of winning, or that of a carry being snowballed, or whatever other advantage there is, but it's a much more rational thought process.

tl;dr Don't take what I said as a cookie cutter playstyle.