The enemy red/blue buff should be your top priority since you need it to win your lane and you are really good at stealing them(since you have equipped smite) and can easily escape with your w. Try to lasthit as many minions as possible and tell Garen to take the ones you miss. Corki does not rely on items so just fight and stay in the botlane/the enemy botside jungle as long as possible until your enemies either ff or you get your first tower, this should happen around min. 8. If you dont get the enemy botlane tower until min. 9 you are doing something wrong.

Sry I cant provide any tips here since I just black out at around minute 12 and suddently regain consciousness at about minute 20 into the game having about 23 ***its.

There is no late game with corki! If you hit minute 30 and havent won yet just go afk and get some food!

You shouldn't really care about Corki's abllities, since your auto attacks will destroy the enemy at about minute 83 into the game. The E has a lot of ultilty when you are stealing your junglers camps (would buy again 10/10). The cooldown on Corki's ult is too long so its not worth it to put points into. Also the same could be said about the packages you get through your passive, since they slow down that much. As corki adc u want to scare your enemies with your madladness since they just wont expect the powerplays you are about to unleash onto them by clicking the right mousebutton.