If going Synology, make sure to go for their 64bit models (I don't think they still sell 32 bits, but unsure); it's needed to support btrfs. Other good brand is QNAP. good quality 2 bay can be found below 300€, 4 bays below 500€.

As the other commenter said you can also built it yourself but frankly configuring Samba and its permissions and updating your mdadm config when changing a drive and all the other things gets boring and borderline dangerous really quick, just know that if you buy a pre-made NAS what you're paying is not really the hardware (you can get better for cheaper if homemade), it's the software.

I like DSM (synology's software) because it doesn't get in your way, it lets anyone use easily yet still offers the advanced options. If you've never had a NAS or don't want to spend hours in config files every now and then, I recommend it.

(as usual the question for devices like this is not so much "how easy is it to set up" but "how easy it to recover if say a drive died and you need to repair your array")

A NAS of course could be a rather cheap system running Linux/FreeBSD with three drives in a RAID-Z1 configuration, with SAMBA server. Then you're not dependent on what fs Windows supports (though I recall there being some work towards supporting zfs on Windows, so perhaps eventually).