Tips to Use Morphling (Dota2)

• As Morph gives +3 to both Agility and Strength with one level, it's a very strong skill to get at level 1.

• As Adaptive Strike scales with stats, it shouldn't be leveled until after Waveform is maxed and should be the last skill maxed out.

• Boots of Travel is a commonly built item on Morphling. By using Replicate, then teleporting back to base, you can then instantly return to where you were with Morph Replicate. This strategy can also be used with Town Portal Scrolls.

• Ethereal Blade is the most common and recommended item for burst damage on Morphling. By Morphing points into agility, he can cause massive damage with Ether Blast, and then use the amplified magic damage to finish an enemy off with Waveform and Adaptive Strike. This is sometimes referred to as the "Shotgun combo". However, do not build ethereal blade if Morphling lacks farm, as this item is most effective midgame, building it too late would not be useful.

• Sometimes deciding which hero to choose for Replicate can be difficult, however potential candidates for this spell include: a hero with high DPS, those with favorable passives (such as Axe's Counter Helix) or even an enemy hero who has a Radiance or some other aura, which allows you to take advantage of receiving its effects for free.

• It can be difficult to determine whether a Morphling illusion is real because it does not take any bonus damage unlike every other illusion in the game. You can use this to try and fool opponents into blowing long cooldowns.

• Morphling's early game damage is relatively high with Waveform and decent right click through Morph Agility Gain. Consider laning with an aggressive support to grab some early game kills so you can accelerate your farm and reach your late game faster.

• Morphling functions better as a carry in teams with a strong front line. This allows him to remain in the fight with a high amount of agility and hence right click or Adaptive Strike damage, without feeling the pressure of being focused. Although he is good at soaking damage through Morph Strength and items such as Linken's Sphere and Eye of Skadi, he is much more useful as your team's primary source of consistent damage. 

source: http://dota2.gamepedia.com/Morphling