Guys, how do I do good as Corki?

build a trinity and the usual AD carry items
10% bonus true damage as a passive is bananas

NO trinity unless youre raping

and ya inf edge - phantom - LW/black cleaver - Bloodthirster etc carry items

But how often should I risk getting close enough for gatling gun?
It always seems to be the death of me.

So AD blitz>AP blitz right?

No.

So in a 1vs1 blitz mirror match AP wins.Great.

In a 1v1 match where two Blitzcranks at equal level, skill, and items were to fight, the AD would more than likely win.
HOWEVER.
When you play AP Blitz, you bring overall more utility to your team.
Also you can get a DFG and instagib squishies if you land a grab.

also youshould usually ignore most AD carries' abilities lategame if you have to get in closer than autoattack range to use them
thats why I dont like triforce on corki

i like it for the sheen and phage passives
i mean you can scrap it for a mallet to make yourself tankier but its all up to you

or you could build like a human being and build like a carry with inf edge bt PD beserker's last whisper and another PD or BT

Do you guys find Rammus a pretty good character? I've been playing as him recently and i've been doing pretty well in games.

rammus is p cool

Rammus can carry low elo really easily

I don't think I've lost a single game as Rammus.
However, I only play blind pick.