It depends a lot on where you are vitamin wise at a base... If you get in at some point to a GP/PCP get them to run basic vitamin + CBC panel + 3-4 of the thyroid panel [TSH, T3, T4, there is another but I forget I think it is linked to hashimotos] + diabetes screening [fasting] if you haven't had one in a while. It's good even if your access to docs is limited to get basic tests when you can. If you have joint pain in multiple joints I also suggest you get a rheumatoid panel once in a while, even though it isn't definitive or diagnostic necessarily.
I have heard but have not experienced relief as some have from these:
B6, MTHFR related metabolizing problem for this, so some find supplementation help, some have linked B6 deficiency to depression and there is a "prescription" version in the US now for this that costs about 10-15x more then just buying the supplement. *Note: I have heard reports from one or more [thanks cog fog] that this can induce mania or psychosis in some very very rarely - the person who reported this was dx bipolar before. I haven't tried this personally yet.
CoQ10, Some people have luck with certain forms of this, a lot of people into mitochondrial dysfunction are into this. I have taken it and not noticed much difference with it, I personally stopped because I'm hoping to get in for a tilt table test (for POTS) soon and have heard it can interfere- do not know how true this is.
B12, pernicious anemia, some people even with normal levels of B12 in the blood have reported they felt better getting high dose shots of this from their docs but that has been banned in some states now, personally it (reg tablets/sublinguals) doesn't make a difference for me and my levels are normal- but if you have a deficiency (P. Anemia) you can get plaques on your brain among other nasty stuff so it's worth getting this checked once in a while... It's said vegetarians/vegans are more likely to have this, but I have found it's pretty common in the general population as well.
I am more wary of herbs then I am vitamins honestly, unless they are very well recognized as safe like culinary herbs [ginger, mint, tumeric]. You might want to look into the blog "fed up with fatigue" I think she may have listed some things for fog somewhere once.