In my opinion, you should buy and wear the colors and finishes you like. But, it can be helpful to understand traditional jewelry styling advice in making (and defending) your jewelry decisions.
"I know I should be wearing silver for my fair skin tone, but I chose gold to complement the undertone today.."
The Vein Test: An easy and intuitive tone test is looking at your veins' color: if your veins are green, you have warm skin tone and should consider gold jewelry first, if your veins are blue you have a cool skin tone and are recommended silver.
If you know exactly what kind of skin tone you have, there is even more detail on which jewelry shades work for you:
Fair Skin Tones: Silver jewelry tends to work best on fair skin tones, as it provides a crisp contrast against the skin.
Olive Skin Tones: If you have an olive complexion, both gold and silver jewelry work.
Medium Skin Tones: If you have a medium complexion, gold jewelry will complement the natural golden undertones in your skin. (Or rose gold)
Dark Skin Tones: For those with dark skin tones, silver jewelry is the traditional recommendation for the contrast. But, increasingly gold is becoming popular to complement the skin undertones.
In summary, you can pick whichever color jewelry you like, but, if you want to abide by the classic color/tone principles, go with gold for warm skin tones, and silver for cool ones.