Gold is for servers. I have one and it's supposed to be extra reliable.
However it is kind of loud and annoying. Thank goodness I only use it to run back up's at night.
WD Blue is fine for most people and WD Black is a high performance HDD.
I don't really care if my HDD's are high performance. That's what my SSD's are for.
I have reliable 5400RPM WD Red and WD Gold HDD's in my System.
TBH I don't notice any performance hit using a "slow" HDD for long term bulk storage. Documents, Pictures, Videos, Downloads, Music.
Western Digital, Hitachi, Toshiba and HGST (owned by WD) are good drives.
I avoid Seagate. Every Seagate drive I have owned has died.
In fact, the only drives that have ever died on me have been by Seagate.
Other swear...