We are able to build one of the following upgrades. Please review and leave a comment if you have a preference.
Dry Dock Expansion 6 - additional -3% to post battle service costs (general savings to the whole clan)
Steel Port Expansion 1 - extra 5% to Steel received (mostly obtained in ranked and clan battles)
Steel for me is not mostly obtained from ranked and clan battles. It is earned from the 6-part daily mission. Completing step 5 gets you 20 steel. Step 6 is another 20 steel. So that would boost it to 42 a day from 40. Over the course of a month that’s another 60 steel.
A tiny amount, to be sure, but better than another 3% creds. Don’t get me wrong, I am eternally low on credits, but I have many ways to increase credit gain (Premium time, focusing playing premium ships, several different signals, convert gold to creds, etc). Steel can only be earned AFAIK.