I've been trying to create a servant of Waukeen, but it's harder than I thought. The suggested domains are knowledge and trickery. Those don't feel right for me because knowledge seems more bookish and trickery would make him look more akin to a swindler. I wanted to create a PC that followed Waukeen's tenants. Mainly: Make money, invest, and spread the coin. I saw a couple good homebrew options, but I want to try and stick with official materials. I don't know what one D&D will be like, but I hope they make a wealth domain, even if it's just mean wanting one lol. In the meantime, anyone got any suggestions?

Have you considered the Order domain? Currency-based commerce and economy require an agreed upon rule set to facilitate transactions as well some sort of legal system to enforce those rules and settle disputes. These are all expressions of civilized society i.e order. 

Thats not a bad idea. Someone also suggested a forge domain as well. Glad to get these suggestions, thanks!

Peace domain could work. They are about resolving conflicts between nations...and it is easier to trade with a peaceful nation. I actually think knowledge and trickery could work too. Knowledge of nations, economic situations, import/export, laws, etc help you to better trade. A shady trader would take trickery.

Forge Domain.

It gets you Fabricate. Which is basically D&D's "Infinite Money Cheat Code".

If you multiclass with Druid or Bard, or whatever else gets it, get Plant Growth and watch dis 'ere youtube video by the mighty Bearded One (DND Shorts) to piss off your DM and utterly annihilate their world's economy: 

Right, I watched that yesterday. He uses flax, but really all that is used in linen is the stems. The seeds could be used to fabricate linseed oil from the same crop (you'd need barrels or jugs to fill I guess).