Preferred lane: MID
Why? As a ganker, your job is to get fast levels and roam other lanes with your burst skill damage. For that, you will need levels over other lanes and runes. For rune control, you'll need a ward at one (or best would be both) of the runespots. Get a bottle so you can refill it with runes and get free regen.
Skill Build: Max out stun + chuck OVER ultimate
Why? As I said earlier, the sooner you get your burst damage, the better. if you get maximum damage at lvl8, you can literally one shot anyone below 900hp (at 8-10 minutes, thats 90% of the heroes). If you get your ultimate at lvl6, you'll get a little bit of a base damage boost, but your attack speed will decrease dramatically.
Item Build: Steam boots OVER Striders
Why? Okey, you went mid and you have a fantastic time: got bloodlust, haven't missed a single CK, thats cool. You got your bottle and red boots, whats next? The most effective itembuild is to get Steamboots right away. If you have runecontrol, you dont need other regen items (maybe power supply), and steamboots can give you more mana, health or attack speed. After steamboots you can rush your portalkey. A well-timed portalkey is around 10-13 minutes.
Item Build: Got portalkey, ggwp. Or wait... what?
You got your portalkey, whats next? Maybe you didnt have a good start at all, maybe you got your portalkey at the 20th minute mark and your team is loosing big time. Most of the players would say: okey time to increase my burst damage with good old spellshards. I mean, the item is pretty good, it gives you mana, faster regen, attack speed and minus magic armor to your combo, but I will be honest: you will be literally useless in fights. Maybe you kill someone with your boosted combo, but whats next? You're just a sitting duck. Instead of spellshards, I recommend Bulwark, later on you can upgrade it to breastplate, or get a shrunken head so you can actually deal damage after your combo without getting killed in team fights. Or get a frostfield plate, the item is so underrated: it rapes melee carries. Or if you're a hardcore one, get a puzzlebox. Just please, dont think about those spellshards unless you're immortal and want more kills. Even in this case, just get a codex. OR Sheepstick, best item, even if it got nerfed in the latest patch.