South terrace + roofing - later conservatory - piling up or floating

Hello,

at our house on a slight slope, the previous plan was to fill up the south terrace of about 10 x 5 m with a height difference of about 1.2 m to the terrain and to secure it on the sides with walls (the house will also be built up accordingly, no basement).

My question would be whether it would be more cost-effective to build a floating wooden terrace.

Since I also have plans for a terrace roof extension up to a conservatory (currently no money for that) in my mind and the budget is very tight, the question would also be whether to leave the terrace incomplete for now and do it gradually afterwards.

When building up, the question also arises whether I can simply put a conservatory on top in 5-10 years or whether it would be better to already lay the foundations plus floor slab for it now, which would then again cost ? €.