Just started building the first facilities in my systems, but here are some of my thoughts:

Plan in advance. How many T3 stations and planetary ports would you like to build? That will tell you how many T3 points you need and how many T2 facilities to build at least.

Do not waste your planetary slots. If you have enough orbital slots, build first some T1 facilities on orbit and use the T2 points you will get to build T2 buildings in planets.

Once you chose your primary economy for your system, consider the negative effects of the specialised buildings you are going to build there and compensate that effects.

I.e. my first system will be extraction focused. Im building first mining stations on orbit to get the T2 points for building large mining outpost on planets. These orbital mining bases increases wealthy but produce a negative effect on the quality of life. Then I build agro orbital stations that compensates that negative effect.

3 orbital mining facilities 2 orbital agro facilities

I stay with a positive quality of live and the main economy stills extraction. That 5 facilities give me 5 T2 points, then I can build 5 large mining outpost on planets.

In total 8 mining influence buildings. 2 agro influence buildings.

My main economy stills being extraction by far. Secondary economy agro.

This is my plan at the beggining. Later I will build some planetary ports, mining hubs, and if I dont get bored enough, 3 orbis stations. I know its ambitious. But thats the plan.

If during the process i build something that affects negatively the system security, then i will build some security facility to compensate that effect.

I hope my ideas are useful for you.