1) Use scouts to find anomaly sites (I try to start my 1st one around turn 5), as they will spawn landmarks and other goodies (sites) right next to your existing territory, right next to your capital.
2) Try to use energy and production exploitations to get early mass unit production, but always play the planet/ what the game gives you. For example, I would go for sectors with celestain artifact or a stadium arcadian if you think that you will be able to easily defend that territory.
3) Get research from anomalies
4) Get food from sites and razing or workers if need be.
5) Get production and energy from your capital’s exploitations (always useful in war, as in right now/ immediately useful). You can support up to 20 pops (-2 per pop = -40, 4 workers = 20 + colony center = 20) without a food exploitation and no rivers.. If you are lucky, you will be able to get +10 food from rivers allowing your capital to support way more pops (things like bread and circus and further boost your happiness leading to more pops being supported)
6) Maybe take one food sector, which you can convert into energy or production later. I would only do this if you didn’t get rivers inside your empire easily.
7) Happiness events are a great way to get more energy.
8) Sending populations from bought or conquered independent settlements is a great way to get population in your capital, especially if you have the decadent vice. The influence cost depends on how many colonies you own, so it’s super cheap if you have positive race relations and you only have one colony.
9) Sometimes, when you are scouting, you see an enemy’s second colony, and by resettling those pops, I can move them into territory that is easier for you to defend. Even if it is just a city that is close to their border, it is better for you to use those pops than to let a hostile AI conquer or buy them while they are independent. If the colony is your starting race, then it will be super cheap.
10) Upgrade colony infrastructure to help defend your sectors (don’t skimp on the resources, investing in this will allow you to defend your territory from wander marauders while your stacks take out valuable sites and/or complete quests)
11) Go to war with one NPC faction and do all of the quests for another. With less territory to guard, you can send your spare stacks to do quests and/or kill off NPC faction stacks that are guarding locations. Attacking the first NPC faction you see will allow you to use your influence on buying settlements (to increase your population in your capital and to annex the sectors around it. I chose to focus on rushing towards a positive NPC faction relationship, so I could spend my influence on units for a better military.
12) Noble Diplomats is a great way to get energy in the early game.
13) Star Union Scholars will allow you to get more early game resources (to support your large military) from the sites that you clear out.