Examine.com is an independent website that documents clinical research on different supplements. I’ve looked through and managed to find 4 cheap natural supplements that are all described as having a “notable (moderate) effect on depression” and are supported by “high to very high level of clinical evidence”. The 4 supplements (with Amazon links) are:
All four are easily available and they don’t interact with each other so you can use all four of them daily if you wish. All four are available cheaply online.