Planetary Annihilation YouTuber AndreasG presents a fundamental build order for maximizing income in the initial couple minutes of play. The economic foundation laid by this build is capable of supporting transition into various strategies. Here I've pulled a couple moments of insight with cross-game relevance, but if you are playing PA yourself, it's certainly worth checking out the rest of the video.
It is important to place the initial bot factory close to the core metal points, to minimize the time the early fabricators ("fabbers") waste in travelling to construct the metal extractors ("mexes"):
A fairly early air factory is important. Air units enable invaluable scouting. Additionally, flying units can be used to harass the opponent's fabbers and disrupt their economic development critical to success in the opening:
A player's commander unit contains a great deal of the metal resource. The ComReclaim build presented here uses a combat fabber to start reclaiming the commander's metal and jump start metal income at the cost of energy and commander hit points. AndreasG makes the important point that one ought to interrupt the reclaim whenever one's collected metal is overflowing one's metal storage capacity, as the excess income is thrown away but the costs (in energy and HP) are still paid: