How do you play Murky? I am planning to buy him but not sure
1) Block or Bribe
4) Living the Dream (occasionally Bigger Slime)
7) Compressed Air (Slime Advantage if you went Bigger Slime)
10) Octograb
13) Bubble Machine (til you get used to him). After that, go Wrath of Cod or if you went Slime talents go Continuous Slime.
16) Rejuvenating Bubble (if you are super uncomfortable with him). Slimy Pufferfish 100% of the time otherwise.
20) ...And A Shark Too if you went Pufferfish. Rewind if you went Slime.
Murky is a hero who is meant to die. You're gonna die. You will die pretty regularly when applying Octograb in a team fight, for example. The point of Murky is that he gets more or less "free" deaths as a resource. Your job is to make sure you use this resource to gain an advantage. Feeding as Murky is bad. Getting killed as Murky while taking out an enemy who counts as a full death? Well worth it. Dying a time or two to stall an objective so your team can win a team fight? Worth it. Dying as the enemy team chases you around the map and your team grabs mercs/objectives? Worth it. Dying as the enemy tunnel visions on you while the rest of your team kills them without a struggle? Worth it. etc etc. If you die and gain no advantage (no secured kills, objective, mercs, what have you), however, that was a bad death and you're just feeding experience to the enemy. It's worth noting most games you'll have a bit of this too, particularly early on and even more so when you face certain heroes like Raynor/Tychus/Nova who seem to love to tunnel Murky and either burst quickly or have fast auto attacks so that your bubble isn't as useful unless you're near your wall).
When you first start playing him, you want to take the bubble talent at 13 for sure (and possibly at 16 as well) until you get used to how to engage and disengage and not feed. Once you grasp that and feel comfortable, drop the 16 bubble talent for Slimy Pufferfish. If you're in a game and feeling really comfortable, start dropping the 13 bubble talent for Wrath of Cod (or the slime equivalent if you went slime). Once you add those two pufferfish/slime talents at 13/16 in your damage and threat level to the enemy goes through the roof.
Harass your lane from 1-10. You are pretty weak but you can clear your wave quickly with Pufferfish + Slime and some auto attacks. Pufferfish will zone the enemy out unless it is a strong waveclear hero. When objectives spawn, remember to move your egg closer to said objective but far enough back that it won't be easily seen where you are returning from - thankfully almost every map has a lot of options for this.
Once you reach ten and get Octograb, drop your Pufferfish under an enemy and hit R to grab them. Ping the shit out of yourself so your teammates hopefully follow up - it might not hurt to explain how it works ahead of time if you are in a lower MMR bracket. You ideally want to target squishies as you can nearly kill them by yourself even at level 10. Don't lose sight of how strong you are for objectives. The ability to die and come back nearly immediately is amazing on maps like Cursed Hollow, Tomb of the Spider Queen and Dragon Shire. It's annoying to attempt to secure tribute/gem turn in/a shrine with Murky constantly there whittling away at your health.
By level 16 if you go the Pufferfish build you can actually kill squishies with Octograb combos by yourself. Even easier at 20 with the ult upgrade. As long as you hit the right target and combo it with your W you should secure a kill all on your own at that point with minimal effort. If you went Slime build you just want to harass and harass and harass some more. Slime em, auto attack em, try to zone em into your Pufferfish, etc.
Really, the TL;DR of this whole thing is harass, harass, harass, octograb delete, harass, harass harass regardless of how you build him.
PS: You are doing the right thing. MURKY THE SEA GOD!!!!!