Beggining with this guide, Pyke needs some help on the farming side.
On early, he will need help on the blue, and you wont be able to do the full clear, but don't worry about that, because you will be farming better when you get the Tiamat.
When you finish your clear, head to the nearest Scuttle and farm it. If you find out the enemy jungler is taking it try to steal it with you Smite but if you have it on cooldown, just leave and get the other.
Remember Pyke has high mobility and that can be incredibly useful against other champions, and also to get quicker to the objectives and stealing them.
When you do your first back, try to have the gold to buy the Tiamat, if you haven't got the gold, buy a Pickaxe instead.
With the Tiamat you'll farm quicker and better, and later when you get the Ravenous Hydra and the Berserker's Greaves you will farm better and as if you were a normal jungler champ.

Getting objectives is more difficcult than farming with Pyke.
You will need a lot of help on early and some help on late.
Pyke has a very little amount of hp and that makes him vulnerable to the other team trying to steal the drake, so you can't solo objectives as Drakes or Nashor.
However, you can solo farm the Herald and use it on your ganks.

Ganking is the most fun on this build. We can accept Pyke is horrendous at farming, and it's infernal to play as him and farm. But ganking is very pleasant, and you give to your allies extra gold, feeding them for late game.
With this guide you wont be able to early gank with a lot of power, but you ally can do the damage. If you want to early gank doing some damage, buy Serrated Dirk right after the tiamat, and you will have more damage.
Well, now let's go to the ganks. To gank as pyke, you have three options:
1- Gank as invisible: Press Ghostwater Dive and go where you want, then hook and stun your opponnent with your Phantom Undertow then wait for your teammate to hit him and ult the enemy.

2- Gank with your E or Q: These two options are less efective on my experience. I highly recommend to use the first, but with these, you can help your teamate to stun the enemy. Use this if your teamate has a stun to use, like Shen on top or Lux on mid

Pyke is a non-optimal pick for jungle, but he is very fun. I have used him a lot of times on ranked and i have won most of the matches, but im on silver, so don't take that wins as an example of Pyke being a good pick for jungle.
I encourage you to try him on normals and tell me your opinions on the build, thank you for reading and, GLHF on your next matches!