Benefits from non-mandatory terraforming projects?

[Elthy]

I started my first terraforming project in Getsu Fune and am wondering which projects i should do other than those in the mission. Some seem to have the effect of reducing the cost of other TF projects (only on the same planet?), but what about e.g. bringing ice to the planet?

[BitByte]

Tasks which reduce required materials affect only that specific planet as they are planet side jobs. So when you move next planet you need do that same again.

Some tasks may be required to complete so you can make planet fullfill further tasks requirements. For example you may need reduce/increase temperature in the planet and increase huminidity and so on.
You can personally decide what suits the best to your playstyle and that you can achieve the final goals.
As eathquakes will affect ongoing planet side tasks (e.g. destroy already delivered materials if construction is not ready) you may want work with those. Keep in mind that earthquake will not destroy ice.

The real optional tasks (like leisure places after habitation tasks) you can freely decide (if them are not mensioned as "required") as those won't affect population but are just for consume extra resources and give you more fuzzy feeling about success.

[RainerPrem]

I started my first terraforming project in Getsu Fune and am wondering which projects i should do other than those in the mission. Some seem to have the effect of reducing the cost of other TF projects (only on the same planet?), but what about e.g. bringing ice to the planet?

You can see the preconditions for each mission in the list, when you click on that mission. E.g., for planting crops, you have to fertilize first. To fertilize you need temperature and humidity in the given color. To lower or rise the temperature you need to do specific missions first.

That said: Getsu Fune is one of the easier missions, but you can start with Memory of Profit, that's the easiest one.

You can look here to see what missions (and how many of each) you have to do.

[vvvvvvvv]

but what about e.g. bringing ice to the planet?

It is one of the ways to increase humidity/water level which is ALWAYS available. There are other ways, but they can only be done limited number of times.