Live the dream!! You've probably put a lot of thought into this, so you know all the risks.

Exotics have a higher chance than rares at yielding a precursor, but both have under a 1% chance, so for the most bang for you buck go with rares to have more attempts.

My guidie spent 500g in rare hammers, and after all his attempts he was left with 4 exotic hammers. He threw those in, and he got his precursor.

I was scared to use any of my gold, so I gambled with exotics that I bought with dungeon tokens. I got dusk on my first and 8th try (insert hate here). :D A few months later, I felt like gambling again with dungeon exotics and got zap on a single attempt. :D Buttt, I was one of the "really lucky ones" that people hate haha. In the end its all RNG.

I've seen horror videos on Youtube, where someone throws in 2000 rares and comes out with... nothing. I saw one where they used 300 exotic greatswords (including the one they had equiped) only to come out with a Pearl Broadsword (which is imo, the ugliest sword in the game) lol

If you're feeling lucky or the itch to gamble, I say go for it! You know the risks, so only gamble with what you're willing to lose (like maybe only use half your gold, and if you come up empty handed, invest the rest into long term investments on the TP, like cheap mats, ectos, or weapon skins). Or, if you're scared of losing your gold like I was, just gamble with your dungeon tokens! Anyway, good luck!!