Help a scrub out

I just installed the game maybe a week ago, the last time I played was around launch, and I didn't really like it so I stopped, but I'm loving the game now.

I've just got some noob questions about some champs that I've been struggling with, and judging by the forums, it's common for nubs and scrubs to struggle against these, though I can't find any concrete, helpful advice.

I've taken a liking to Top lane, and I like playing , and . I'd say I'm decent all things considered at all 3, but when I have to lane against a or (though with Ryze it's more me getting frustrated by his snares), and even worse is when a or help them out on top, I die pretty much every single time. I just don't know WTF I'm supposed to do half the time against a Garen, since he seems to be able to spam out his abilities every 3 seconds and do ridiculous amounts of damage, even in early game, and I can't even escape from the guy.

Though I haven't encountered much of him, also gave me a LOT of trouble when I laned against him some games ago. I was always just left amazed at how much freakin' damage he did to me in just one ability.

So yeah, any help or tips would be greatly appreciated!