@tomsk Do the research, read the hardware guides on the website, follow them, don't use cutting edge hardware (this always lead to trouble, especially network interfaces), and don't take curmudgeonly additudes personally. Invest money proportionally to your time and the importance of your data. And have a backup regime figured out (you can start working on the plan now).
Maybe your first NAS should just be an experiment until you've figured out all of this stuff. ECC RAM is good. There are loads of highly strung enterprise type people on this forum, so take their advice but if you're not in enterprise, if all you're doing is saving disposable data that you don't care about, at first, then don't overinvest. Remember: regardless of how amazing your NAS is, your backup regmine is more important.