Morphling is a high mobility, high burst damage hero that is extremely dangerous in the right hands with the right build. I can't make you any better with Morph but i can give you an excellent build to help you snowball completely out of control and take over games. This build will focus on playing Morphling in a trilane so keep that in mind when i go over your starting items
Mid Game Team Fights
At this point you should have your Perseverance and your Ethereal Blade and you are ready to start picking of those lone heroes and contributing in team fights. This is when Morphling gets realy dangerous. Waveform+Adaptive Strike in combination with Ethereal Blade will let you absolutely destroy supports and more squishy carries in the blink of an eye. You just pop Ethereal Blade on them, Waveform over them, and hit them with Adaptive Strike and they are dead. For those of you who dont know this is the typical "Shotgun Build" that made him so feared and famouse. The reason this works is Ethereal Blade does 75 damage + 2X your primary attribute (agility) and makes them take 40% more magic damage so your Waveform and Adaptive Strike will do INSANE amounts of damage that will infinity scale up with the amount of agility stats you gain. This allows this combo to remain just as useful throughout the entire game. Unfortunately this combo costs a lot of mana. This is why you need your perseverance and Ring of Aquila and Crystal Maidens Aura. All of these things combined will give you realy good mana regen to help you sustain this combo.
Late Game Ownage Time
You may have noticed that by following this build above that you will be buying ALOT of Ultimate Orbs. The reason they are so good on Morphling is that they give +10 all attributes. If you follow this build you will have a total of 4: (+40 all attributes). You can morph most of that to agility making for **** TONS of agility stats. So many in fact that you will have max attack speed, around 300 damage, 40 armor, and a 2k mana pool while still maintaining over 2k hp.... wow. If that still hasn't convinced you that this build is the way to go i dont know what will honestly.
Morphling isn't quite the king of *** kicking he used to be but he is defiantly not washed up (see what i did their? lawl). His early game got severely nerfed and the shotgun build is no where near as fluid (i crack myself up) as it used to be but it still works and he is still a GIANT late game so don't write him off. And for those of you who think he is useless you just suck or have only seen people play him that suck. (seriously i hear that from noobs all the time wtf) Anyway give this guide a shot and and let me know in the comments what you think. If you have any suggestions please be intelligent and explain them with detail.
Thanks for your time and happy pub stomping!