There's an interesting meta-analysis of the antidepressant effects of endogenous neuromodulators that I have read. I'll spare you all the details but it found a number of supplements that appear to have good effect as antidepressants. Of them, the most readily available ones they mentioned were Vitamin C and creatine.

For vitamin C, you're looking at a dose of around 500-1000mg per day although you could go higher on this with minimal concern. At high doses you might have an upset stomach especially if you go too hard too soon on it but aside from that there's little else to worry about.

For creatine you're looking at a dose of around 5-10mg per day. The same applies as above. There's really no need to go higher than 10mg though and you'd probably just waste money by pushing the dose higher than that.

While N-acetyl cysteine is not endogenous nor a part of this study, there's some evidence that around 1000-2000mg per day may also have antidepressant effects. This is another supplement that has the same caveats as above.

For OTC anxiolytics a few stand out: kava (I'd recommend against taking kava whole and instead preparing an extract in water especially if you're planning on using it regularly and making the most of the potential reverse tolerance effect), L-theanine, valerian (I'd veer away from taking this daily and it's something that would be better taken occasionally or for a few consecutive days here and there). I'm really partial to damiana but that's a bit harder to get and I have ADHD so the effects of it on me may be less common. Kratom has an anxiolytic effect at higher doses and I am extremely partial towards it although I'd recommend some caution with it as it's possible to develop an addiction to it so it's another thing that would be best used occasionally rather than daily if you did opt for this.