Originally Posted by PWMTrav

I mostly agree, but (bolded above) OP is not referring to a G fare, and for that matter, fare buckets vary by carrier (for instance what you're referencing as a cheap fare would actually be a discounted business fare on Delta). *G is FT shorthand for Star Alliance Gold status.

*G does have fast track in T3, and I believe LH flies out of T3 for all flights at FCO, but I could be wrong about that. With a boarding pass in hand and no luggage to check, I'd probably be there 90 minutes out, but that's my general rule for larger airports. It usually ends up with some time to mill around or stop at the lounge if there's a decent one (FCO generally being full of mediocre lounges, unless anything's changed).

As for the person asking about the KLM flight to AMS, without any additional detail, I'd say just show up 2 hours early. At least, that's what I do when I have bags to check, no relevant status, and flying economy from FCO T1.