My 2 cents worth; Population is everything. Way more important than buildings and starbases. Without lots of civilians on your planets, you aren't going to be generating much of anything, credits, research, or production. Grow (or build) that population as fast as you can. Second, get those trade routes established, the money they bring in can help till you have a big enough population base, at which point the trade routes are far less economically significant, more useful for the diplomacy bonuses.

don't overlook tourism and trade

Raw production goes right to cash, that's helpful.

Tourism goes to a separate pile, but you have to to increase your influence area, and your capital planet counts double, so build your tourism improvements there and keep conquering planets to expand your influence more.

The major determinant is population happiness- the more buffer you have in happiness, the higher you can raise taxes, and the more money you can bring in.

Before he upgraded he was in your administration pool which gives you one administrator after he retired he is no longer in the pool so you gain 5 administrators but lose one from the pool. However now you can put another administrator into the pool.

convoluted for sure I didn’t get it at first either can’t remember if someone explained it or if I eventually figured it out.

You do not need planets dedicated to Economy anymore, simply build a Port of Call and or other Tourism buildings on each planet and watch your money sky rocket, I have hit 7k bc a turn with the new Tourism mechanics Upsers.com

I am on a Gigantic map and use admin ceners so I have more then I need.

Agreed. My Administrator Training Institute mod works for silicon as well as carbon, if you're willing to use mods.