I made tons of friends when in buildings or boss battles. The game is pretty easy to make friends on as long as you actually talk to people due to there being no real action in the cog battles

The way I do it is by just talking in every facility, boss battle and building that im in. Most of the time people will respond and then you just need to have a likable personality to continue it. If you like the person then send a friend request ASAP and then try keep in contact to see what they need and join in with them

I have found that I made the best friends when grinding out lawbot and bossbot. It's a smaller pool of people doing it so you meet the same people a lot and it takes so long doing the same thing that youll always be around them and talking cures the boredom for me