@nopantsu Sorry to hear you haven't had much luck getting a Gold. Our RNG for the Relics is random, which is part of the reason why we have the Shard To Get Relic (which at least guarantees a Silver with an increased chance for a Gold every 25 characters you earn).
We are planning on posting more about our Relic loot rates in the near future to hopefully lend a bit more visibility (we also intend to have more information available in-game in a future update as well).
It may come as no solace given the investment you've already made, but the best way to "guarantee" a Gold is to compete in the Gold Prize Fight events and score in one of the top Rank Reward tiers.
Hope that helps to clarify what's going on under the hood. Sorry again to hear about your run of bad luck.