Just nope.
Nope. Gauls are more expensive than romans looking at ress per attack point.
their horses use much more crop then others and if you want to bring crop usage to normal point you have to build their special building and that is so bad
Why is this bad? Use the horse drinking trough and you are on the same level. You need it anyways for the production bonus.
their units production speed is 3 times slower
But production speed doesnt equal troop strenght. Oh and by the way, with the horse drinking romans have the fastest training times of all tribes.
and they use 2 times more resources to build
See the second quote. Their troops are more expensive (but not nearly 2x) but they are stronger too.
Only good thing they have is that they can build both resource fields and city buildings at the same time that can be countered by buying gold
Nope. You can buy additional slots with gold but the other tribes cant build a field and another building at the same time.
Particularly for big hammer builders who are training their main army for a couple of months the cost of keeping building round the clock as a Roman is cheaper than as a teuton.
No its not. But the upkeep for the roman is lower.