before the game even starts, during the pregame lag, I buy 100 crs, sell 100 metal, upgrade civ infra, build a cap factory with one builder, set the other builder to the crystal extractor, and cue the other two metal extractors, and build 2 scouts. In virtually 5 seconds I've effectively spent all of my starting game income. I find that this sets me up for exploration, gets my cap ship out as soon as possible for expansion, and helps set up my economy with the extractors and the planet upgrade.
i do something very similar although i usually dont sell any metal (probably should considering how much i do it later). upgrading civ infra is very good to do in expected long games but in short 1v1's or if you're expecing quick rushes i prefer to put it into other things as it takes something like 20-25 minutes for you to have made back your resources that you invested into it.
i also salvage my cap ship factory after i have built my first cap (usually the mothership as advent). i'm not going to be getting another cap for a while and having a few more resources and an extra logistical slot on my home planet can be really useful.
