Hard Carry Panda build which works a lot. Recommend Going mid because panda is great midder and has great mid control and rune control, even bigger if you have your early dagger after getting your ult you can easily kill mid unless you are facing like qop or just gank top and bot for even easier kills. When i Say hard carry i mean going for Armlet Assault and Bfury And basher. The core Aghanim and Dagger i usually dont go when playing really carry i almost certain do it when i go mid brew is obviously great ganker even more with dagger and aghanim and is ult is one of the most feared that's why he is usually countered by rubick.

DONT GO MID PANDA IF YOU ARE FACING A SILENCER I ONCE DID IT in a team matchmaking with my friends and we did win but i turned to an initiator support panda because i couldnt do much.

Tips to master the mighty Primal Split:
Introduction- Use the Tab to quickly switch the pandas so that you can micro them better. (recommend this also for Chen)
1st tip and the most important: Always use the stun with Rock panda it's the best and the thing that makes u almost ever kill one hero at least when ganking. It has a lot of range although the rock panda is really slow.
2nd tip - Always cyclone the anoying hero of their team in a team fight for example enigma or tide or nyx or other guy that might cause some troubles in a team fight (big aoe guy ). Also if u are ganking 2vs2 or 2vs1 if your fed then cyclone one, focus the other, kill him and then dispel the other or just wait but dispelling is quicker and kill them.
3rd tip- When Running away send earth back and put wind panda cycloning and use wind walk while blocking the opponent. Wind walk can also be good to last hit one guy like squishy supports CM or Wisp.
4rd tip - Mini Radience Haste Fire panda. He's really fast and really squishy but send him to finish the wounded one's!

Here it is Enjoy :D