Affordable garden in new construction - how to proceed best?

Uh, sorry. You're talking about a double rod panel fence and want privacy? Any properly planted hedge, whether with hedge plants or shrubs, will be opaque in at most 4 years. A fence does not provide privacy. Maybe you should take a walk through a finished residential area with open eyes ;) By the way, a lawn is the most maintenance-intensive thing a garden has to offer. You can't get a meadow from a roll.

If anything, privacy strips would be put on the fence,

it is then opaque. What is the difference between lawn and meadow?

That’s not a garden what you’re planning there.

100 euros per sqm for paving including materials and installation I consider too cheap.
Pay attention to the instructions of the general contractor on how the terrace must be constructed towards the house.

Spray protection strip is missing
You mentioned gabions but didn’t list any costs

Meadow contains wildflowers, herbs, grasses like red fescue, German meadow grass, smooth-stalked meadow grass, meadow foxtail – what lawn lovers would call livestock fodder.
Roots grow deeper, don’t have to be kept short permanently, are not so sensitive to drought.
As a barefoot/play area I wouldn’t sow wildflowers and herbs. It will never be as soft as a perfect golf lawn.

You can sometimes get plants on eBay for pick-up, free cuttings, offsets, divisions among friends/acquaintances, neighborhood, relatives.
Norma, Aldi, bargain markets sometimes have quite good prices

Remove sod and sow yourself.
Remove gabions.
Own work
are the saving points.

Google improvement of microclimate for example Nabu or get the Kraut und Rüben magazine from 1-3/2021. Hot summers that heat up the terrace and house are becoming increasingly an issue. With clever design a lot can be improved.

:eek: :mad:This is a total desecration! And ugly because it doesn't fit with nature. Anyone who has such things here won't make any friends**.

Meadow is with weeds and wildflowers…
**… but I'm out of here with my tips!