feral scream is a good harassing abilities in early game, with its long-lasting silent(2 seconds) and moderate damage.
vorpal spikes is a good farming tools. Try to push the opponents to their turret by feral scream and basic attack ( vorpal spikes ) . with a good dps is a piece of cake to push them to the turret.

usually i get 4/0 - 7/0 in early game, but basically most of the gold i get come form minion. I usually get 50-90 minion kill before the first teamfight,taking small-sized ganking out of account.(small-sized = 3-5 players)

in this build, the most important element is HP. Try to get your ulti to full stacks as soon as possible, use it on minion if time allows you to do so. Thats increase your hp drastically. The equipments will give you more hp. usually I get to 5-6k when i enter mid game. It is quite enough for early-mid game ganking.

In late game, you should have completed most of the build. That gives you about 6k-8k hp taking the ulti into account.

You SHOULD be the initiator of the team. Be relax when you initiate the fight. Do NOT use your Q and W when you just initiate, as most "tanks" do. Try to use your ulti to get some last hit, that gives you some extra gold to finish your build.

In a team fight, your Q should be used in the end period of the fight, which helps in escaping and chasing enemies.(since it has a slowing effect) Your W should be used when some enemy champions are using some long-lasting ulti or charging for their ulti. For example, Nunu, miss fortune's ulti could be stop by W immediately after they start it. your Q can also has the same effect, but the charing time for Q is too long to stop their ulti in time.

Your ulti has multiple use.
First of all, your ulti helps u killing champion. It does TRUE damage, which means that you could give them a great surprise when both of u are in low hp. This especially helps you to harass Tryn in early game, since he will not expect you to suddenly kill him at 200+ hp. Most tryn cant get their ulti up if you are skilled at this trick.
Finally, your ulti has a growing effect, getting a full stack can "grow" you to a "full size". This helps in tanking, since your opponents can hardly click on your dps, who is near you and "covered" by you. If you dont believe in this, try it out. It is always interesting to hear your enemies complaining that your big size hinders their attack.