1. Waveform
2. Adaptive Strike/Stats
3. Waveform
4. Stats
5. Waveform
6. Stats
7. Waveform
8. Stats
9. Morph
10. Replicate
11. Replicate
12. Stats/Adaptive Strike
13. Adaptive Strike
14. Adaptive Strike
15. Adaptive Strike
16. Replicate

Justification (Flexibility): This is an experimental build with the goal of achieving the most flexible type of Morphling. It can be adjusted according to every situation. You can adjust it your liking, beyond the two obvious changes you can make.

Waveform is maxed first as it is clearly his best skill. It will be his damage source from early to middle game, while still being useful as a utility spell for ganking and escaping. It costs 165 mana, so we only take Adaptive Strike as his second skill to interrupt.

His manapool is quite low, Stats offer a good fix to this. So only take Adaptive Strike early if your allies' stuns are too valuable to waste on a channeling Hero. Otherwise, head directly for Stats up to Level 8.

Morph costs 20 mana, and we only need 1 level of it for now, taken at Level 8. It will be useful for manipulating your stats slightly. You then level the rest of Adaptive Strike during 12-15 because that's where it'll be likely to be effective.

Replicate is taken at Level 10 and 11. Although it is not as important, utilize it during those times!

If you have not yet read what I have been trying to imply earlier in my foreword, this skill build is not meant to restrict your gameplay. Flexibility is Morphling's greatest asset, and to provide only one skill build to use limits his potential. I've elaborated on the Miscellaneous portion about situations involving a change in the skill build, but so far, this is the most common build that I personally use.

Note: Adaptive Strike is taken early only when there is a need for interrupting channeling spells and that's it. Otherwise, go for Stats.