Optic Fiber remains one of the best attachments in the game, I literally always use it.
Yes, you are limited in what you can do without the 100jp or 1200jp gifts. 100jp is needed to really start doing things, 1200jp gives extreme amounts of flexibility.
Generally:
All Auto repair kits
All Armor Plates
All Mana Jammers
Heatsink(Depends on your gear)
These are useful regardless of whatever else your Automaton is doing.
Valor Edge
Strobe 1+2
Inhibitor 1+2(One of the best attachments in the game)
Turbo Charger 1+2(Also one of the best)
Target Marker(A must for high level content)
Coiler 1+2
All Tension Springs
Attuner(Specifically for Overdrive zerg)
Stormwalker
All Mana Tanks
Mana Converter
Tactical Processor
All Loudspeakers
All Tranquilizers
Vivi-valve 1+2
Damage Gauge
Mana Booster(Situational)
I don't think you should look to other people for Automaton builds. The way you play PUP really shapes how you should build your automaton. Different situations require different builds to be effective. It's better to understand what each attachment does and when it is useful or detrimental. Understanding what you are trying to accomplish and focusing in on that is another key aspect of building your Automaton properly.
PUP IS NOT LIKE OTHER JOBS, YOU CANNOT JUST FOLLOW A GUIDE AND GET GOOD RESULTS.