Basic supporting tip: play like you have to farm
I see this SO often:
"I am a support main. I'm in bronze because my ADCs are stupid, look at my KDA I never die and I ward all over the place!"
Then I go "here let's play a game I'll see if I can at least help you get up to gold, I know I'm not great but bring in bronze must suck" and then we get into lane and they're off in the bush, sitting, waiting to fire a max range Nami bubble or hook, and their carry misses farm because they take harass if they try to go up and get it. And on top of that, I get to be all over their carry so they get killed left and right and post game they go
"See what I have to deal with?"
So guys. Here's the deal. As a support, you want to play like you're an ADC. Pretend to CS. Move up within range of the minions, poke the enemy duo if it's safe, back off a little, poke a little more... If you see an opportunity to use the bush to get even CLOSER, do it, but don't feel tied to that bush. They know you're there. You're not being sneaky. A Silver+ Duo isn't gonna magically forget you're there and move out of position, the best windows of opportunity you're going to get are micro-windows. When the carry moves up to CS. When the enemy support backs off to ward, and they're out of each other's auto range for just a second. When the wave shifts and there's a gap for your skillshots. They are tiny, tiny openings and you need to be close to take advantage.
So if you're stuck in bronze as support, ask yourself "how frequently do I threaten the enemy carry? How frequently do I make sure my carry feels safe to farm? How often am I right there on point when a little opportunity presents itself?"
and I can't hit anyone without being dealt three times more damage. Leona is a great hard-engage/CC-nuke champion but her harass capacities are inexistent.
Secondly, the bush: being in the bush is obvious, but what you are doing in there is unknown. Even though someone knows you're hiding in it, you are STILL hiding! Plus, being in the bush gives the control of the bush, and as long as you have the control of the bush, you have anti-push power. A rarely get out of the bush, except for targon's execution and when the enemy botlane has a lot of colliding skillshots I can tank.
What I mean is that being Support can mean many different things in term of gameplay, and you're generalizing the Support role with lane-poking, which is not true.