Ideally one that can use more than one disk so that i can expand it later when i can. Have some minimal experience with Synology since there’s one at work and i have interacted with it a couple times and like the interface, but am not married to any brand as long as it works.
Located in EU if it makes any difference.
the old PC thing is a clear first choice. Also a WD NAS, preloaded with Hard drives have a very good prince point if you also need the HDDs e.g. The WD My Cloud EX2 with 2x6TB HD is currently 422€ (amazon spain) and each individual 6TB WD red is 200€. (leaving the NAS at 20€). If you get the 24TB version is even cheaper than the two HD combined.