Well, I'm going to go against the "rush pkey as fast as humanly possible" grain. Here's the thing. Team fights don't tend to start happening until 15minutes. Ganks may happen, but it's VERY rare to see a team fight before 15. Against 1 or 2 opponents glacial blast is more than sufficient in a ganking situation. So, my focus then shifts to how do I maximize my potential in the first 15 minutes, while still getting my pkey by the time the first team fight happens.
1.) Always be double stacking the pull camp and giving your (likely) solo pulls ensuring they stay near tower for safe farm/easy ganks. Keep in mind there are 2 pull camps if you're on top lane.
2.) EVERY time it's viable to gank do so. Even if you fail you're going to keep the lane on its toes and make your solo's life easier.
3.) Give yourself a defensive/gank ward at all times. If you're playing against remotely capable people they will gank you. Having a solid defensive ward up will help you and your team. If you're legion I suggest the rune vision spot to the right of your top most neutral spawn, and as hellbourne I usually keep one between the the two pull camps.
4.) If you have a carry/semi-carry with an AoE (valk is a great example since she tends to run the solo lane in this situation, heroes like CD, FA, etc.) try and keep at least one camp triple stacked as often as possible. Let them know when you've triple stacked and shift to the lane while they go and clear it. They'll come back at least a level higher for an easy gank.
So, tl:dr, focus on supporting your team and get the pkey as soon as you can. Use the fog to gank early with glacial, it has great range and you certainly don't need a pkey to utilize it. Getting a pkey 4-5 minutes early is useless compared to causing 2 enemy heroes to be under leveld, under farmed, while your solo cleans up.