dear adc mains..
you really should be learning support.
if you really want to improve at adc, you cannot ignore the fact that you are going to be laning with and against a support every game, and you do not know their kit as well as you should.
sure, you know what their abilities do
but what are their cooldowns? what's the range? how can you exploit missed skillshots, how safe are you if your support misses a skillshot?
can you read the enemy support's movements? can you tell when you're being heal baited vs when their healing ability is on cooldown?
just some things to consider. as a support main, transitioning into learning adc has been easier because i know these things like the back of my hand.
and 
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with the occasional 
if we lack any hard engage (ahem) or a ton of cc, and support is squishy as f, so it can't be thrown in. How does Maokai and Vel'Koz support work? and what can I do to counter those lanes as well?
does pretty well against leona from my experience. there's a brief period where you can blink away after she jumps on you and before the stun hits you, and you can hit it just by mashing the E key during her initiation.
support in the past, the saplings can be used for great zone control and you can initiate and peel very well with your other abilities. against him, you can negate his poke by staying in/very close to your minion wave and using them to take sapling damage, forcing your lane to be pushed and potentially having him accidentally steal CS from his adc.