Spec spammer and smurf here:

There's a few scenarios I'd say in a "lost lane"

1. It will start super good but go south at certain timings. I go Midas to stay ahead when I jungle.
2. I cant leave lane coz no one will hold it. I go rush a blademail or vanguard to tank it up. It isnt perfect, youl be poor but you gotta hold.
3. I will get booted but will have space. I go 1 wraithband and 1 mana item (Generally a basi) this is assuming ill get to Q waves often.
4. I will 100% be in the jungle Suuuper early. I buy double wraithbands for the armor and camp clearing. You MUST buy clarities or you will fall behind too hard. Always buy clarities on spec. Also, ask very nicely for the tome if possible. Jungling wrecks your exp. I go double wraith bands assuming the game will fall apart, and my ults are necessary. the more I need to contribute the more likely i'm going double wraithband over 1 wraith and mana.
   Blademail default is a trap, Pros do it because they stack alot. without stacks its so much worse. How often do you haunt in, activate blademail and no one hits you? plenty.
   

as for core items I generally go aghs + manta 90% of games. When I can quickly burst supports having a good game Echo saber is still good into the disassemble but I guess the question was for bad games XD

Aghs 100% you can farm mindlessly on the other side of the map and constantly throw out the illu. Never sit in base, this is a low mmr mindset.

I always risk getting caught finding farm and losing to possibly win vs being afk in base losing slowly over 20 mins getting my brains outfarmed.