This is for the CM game 7262980053:

1:15 - should have pulled small camp
1:50 - should have stacked small camp
2:00 - there’s rarely a reason to skill mana aura 2nd point, as you can just buy more mana regen. Having nova + frostbite lvl 2 is an incredible power-spike, more damage/control than almost any other hero in the game at that point in time, and you just wasted this timing. Skilling it at lvl 3 or 4 is almost always better.
3:25 - should have pulled large camp
3:30 - should have checked lotus (small pull would not have been necessary since you pulled large)
3:50 - pulling small would have 1. not been necessary because you pulled large at 3:25, and 2. is not necessary anyway since creeps are pushing into enemy tower, which means afterwards, since you’re in safe lane, the creeps will meet at your tower again (you actually see this at 4:00, where the enemy creeps are walking into your tower because you pulled). Instead, you shoud have used the creeps to put some pressure on the tower. Also, as you noticed, you can’t really leave Riki alone in this lane.
3:59 - you’re very bold warding the exact same spot that just got dewarded again, especially while you’re under vision where everyone can see you warding.
4:00 - should have moved your lane creeps either to the still living range creeps or into your small camp to your other creeps, not into tower. Now you’ve got a double wave pushing out again.
4:15 - use your spells to lasthit if you are full mana (or learn to lasthit better). Any gold you can get is incredibly important on supports.
4:38 - should have pulled large camp
4:50 - you have very weird camera movement. do you press some kind of “center on hero” button all the time? Idk if that is the cause or whatever, but you could have attacked like 2 or 3 times more if you actually attacked on your attack cooldown, which would have definitely killed SF.
5:10 - PLEASE lasthit the creeps. You can’t waste easy gold on the map. Collecting gold is the most important thing in dota.
5:45 - always try to hit as many enemies as possible with frost nova, would have been no problem here.
6:10 - you just killed both enemy heroes. There’s nothing dangerous here for you anymore. You can do what you want. Pull large camp immediately & farm it. Get the 6 min lotus. Use your healing salve immediately on yourself. Rotate mid or bot through twin gates with your full hp + full mana. Even steal the enemy XP rune at 7:00. Instead, you do essentially nothing until 7:05. Riki could have pulled himself and was under no threat since he had a ward, you would have likely been able to TP back by this time after your rotation or whatever you decided to do.
7:06 - Your ward that was just dewarded earlier at this spot is dewarded again. Surprise ;)
7:10 - lasthit. don’t. waste. gold. your riki wasn’t going to get it.
7:42 - no reason to push the wave in even further with your nova. keeping the wave at your tower is the most important thing against kill lanes.
8:11 - and you actually ward the same spot AGAIN :D
9:10 - could have easily frostbitten SF
9:15 - SF just TP’d out, he’s not coming back for at least 30 secs. Why do you back off against a single pudge? Pressure him, the tower, lasthit + deny everything. Instead you just let him farm and walk in circles a bit.
9:55 - should have pulled large
10:00 - if this move came 20 seconds earlier in time for the rune it would have been really fucking good. Like this you should not have bothered, and at least immediately went back to top. Your riki can do effectively nothing when you’re gone, but with you, you actually have a fighting chance. I mean Pudge+SF are terrible so Riki gets a solo kill anyway, but you see as you rotated back, that kill would have worked against better players as well, not just against terrible ones.
11:50 - Riki is terrible for leaving top, but again, you can’t waste gold on the map. Either you try & tell him “riki farm top” or you should go yourself to farm it. You skilled 1/3/1 which is suboptimal for this, so it’s not terrible that you went bot with your stupid team. But if you had gone like 2/2/1 into more points in nova later, you could farm & push all these waves much easier. Honestly, frostbite’s value decreases the lower in MMR you go, because people are just so absolutely terrible at farming & pushing creep waves so you will always have to be the one to do it. It’s almost always better to skill more nova than frostbite. At higher MMR it’s more of a choice which one you want to go, since your cores don’t leave gold laying around the map as much.
12:30 - absolute number #1 priority, nothing is more important than this, ever, it’s almost worth dieing for this: DEWARD THE ENEMY WARDS IN A FIGHT. Vision is the most important thing to win fights. Who has vision almost always wins against whoever does not have vision. The enemy is also bad at this, but you could have dewarded at the very beginning of the fight easily. Also yeah, you can’t stand this far forward as you noticed. You always have to have your team between yourself and the enemy team at all times as CM. Split second decisions matter a lot in fights.
13:20 - Should have went top or bot, waves are pushing in and can be farmed. Likely bot best because of 14 min XP rune. Could have stacked ancients as well at 14:00.
16:09 - you would’ve been just as fast walking ;)
16:25 - sentry first (almost) always
16:45 - that’s what tranquil’s are for, go stack ancients and let them regen you

I zoomed through the rest a bit more roughly:

~18:00 - You don’t have anyone that can farm massive stacks well. Should have pushed top instead or farmed something else yourself or whatever.
~19:30 - Stacking is more of a downtime activity. You need to play with your team if possible, Riki got a solo kill, but if you had followed him and dewarded it’d have been better.
20:50 - Should have pushed the wave if no one else is doing it.
21:00 - You basically stand around for ~60 secs. Already stacked a bajillion times and no one wants to farm it. Time to go push top instead or farm some with your ult or sth.
25:00 - Always have a ward with you when you smoke. Smoke=Ward, almost always. you could have warded deep at 25:20 in their jungle with that.
26:40 - Push out the wave with a nova. You put too little emphasis on pushing waves out. Pushing waves is incredibly important since it gives vision
31:40 - No reason to keep pushing 4v4 with your carry dead and theirs alive. Split up and farm. Mid and top both need pushing. Predictably, you lose the fight without your carry. Set up for Rosh as soon as your carry is back.
36:00 - Still no one has pushed top, as a result SF gets T2 for free. And 50% dmg on T3.
38:40 - Perfect time for Rosh. Most important objective on the map. No one cares. No one pushing out bottom.
42:30 - Radiant takes Rosh and they win the game. Another surprised Pikachu face ;)

You should have won with Pudge abandon. You lose because Viper+Riki are useless and build shit items and PA is not. Viper should have gone Bloodthorne and Riki should have gone MKB. You have to counter PA with items otherwise she’s unstoppable.

Key takeaways:

• Gold is the most important thing. You are position 5, that means you’re the fifth priority to get gold. It does not mean that you want gold any less than pos 1-4, it just means they get it first. That means if your pos 1-4 are not farming something, then it’s yours, and it needs to be yours! Every pull you do should be farmed (that’s mostly why you pull in the first place, gold + xp for you), every wave missed by someone else should be yours, etc etc. A CM specialty is just Frostbiting a random large creep while rotating around. You need to look for every way to get more gold onto your team, that includes yourself.
• Push your advantage, always! One hero off pulling/dead/whatever? Pressure the other in lane! You’re simply stronger (e.g. lvl 2 power spike)? Push them away from their farming locations: lane/jungle/whatever!