I generally make my first large fleet at nuclear pulse, then run out of fuel training them up, by the time the fuel problem is over I'm replacing everything with new ION designs which are so much more efficient that I have overabundant fuel again.
Right now, early ION, 25 years in my fleet is around 374k tons.
9,000 ton destroyers x16
6,000 ton Ammo ships x6
6,000 ton light carriers x 3
6,000 ton sensor ships x2
4,000 ton frigates x16
4,000 ton sensor ships (spotters for the frigates) x4
3,000 ton corvettes x 24
12,000 tons of fighters.
These are all obsolete nuclear pulse which need replacing, my yards at the moment are:
N - 4 - 16,000
N - 4 - 10,900 -Expanding to 16,000
N - 6 - 5,292 -Expanding to 6,000
N - 6 - 2,284 -Expanding to 6,000
C - 6 - 132,000
C - 3 - 132,000- Adding slipway.
I have another 2 naval yards in construction for FAC's to replace the one that is now expanding to 6000. I can't expand much more than this as I have barely 25 million people to spare on earth, I may have to start moving industry to mars to combat their unemployment.