After all your game starts from level 3, when you have your w-q-e combo.
In most cases your lane opponent will be at (at least) half hp after you charge him (with w activated), do a few autohits and use your e to back out. From this point you just have to wait for your cd's to refresh and kill him with ignite.

After you went back to base and grabbed your blasting wand, you push your lane, get the blue and roam the **** outta da lanes!
If you want to raise your elo you have to secure that at least bot is winning.
Get fed or feed your ad with kills is the most common way to secure elo.

If you are able to catch an early Deathcap, DO IT!
Most of the people will tell you that its way too risky, I tell you its the only way to keep dominating.
Bursting the enemies ap or ad with a 3-shot-combo isnt the worst.
With an early Deathcap u can easily towerdive without taking any damage.
(Everytime your lane is pushed u counterpush, by carefully taking all the cs and keep on the terror on top and bot)

If you do it like i told you,
theres no late (surr @ 20).

If there is: take GA, 2-shot the enemy ad, get killed, let GA proc, e out of battle, go back in.