Hi
@DoubleBubble - here are some things that have helped me:
Andrographis - immune modulator - I believe it helped raise my NK cell function and also has helped with numerous sinus infections
For energy:
branched chain amino acids - these cut my PEM recovery time by more than half. I take about 6000 - 7000 mg a day.
@ljimbo423 takes 10000 - 13000 mg a day (I forget exactly how much!) and they have helped him a lot, not just with PEM
thiamine (B1) - gave me a very nice boost in energy for 1 or 2 days, and then was hit with severe fatigue, which was from my phosphorous tanking due to refeeding syndrome. I discovered this through trial and error. In any event, drinking lots of kefir (high in phosphorous) and later switching to a monosodium phosphate supplement took care of the fatigue and I was able to happily keep taking thiamine. I take the phosphate 2 - 3 times a week.
P-5-P (bioavailable form of B6) - Nutreval testing showed a severe deficiency despite having taken a B complex for many years. So when I added in B6, I had a noticeable boost in energy, though not as dramatic as thiamine did for me.
methylfolate - I'd taken methylcobalamin for many years without noticing any benefit When I added in methylfolate, within 1 or 2 days I felt better than I had in years, and then a day or two later was hit with severe fatigue, this time due to my potassium taking (thanks to Freddd's posts so I knew what was happening). I started a potassium supplement, titrated up to 1000 mg a day in divided doses, and this fatigue went away and I've been able to keep taking methylfolate
methylcobalamin - I'd been taking it for years, even pre-ME/CFS, but didn't notice anything until I worked up to 10,000 mcg. a day (two 5,000 mcg doses) of liquid sublingual methylcobalamin, and then felt a slight boost in energy
Many people swear by CoQ10 though I never really feel any different taking it. Actually one time I did. Someone had posted that grapefruit juice had helped with utilization of CoQ10, so I gave it a try and was drinking at least 16 ounces a day, and sure enough, had a nice boost in energy, which slowly ebbed away, and finally I was more tired than ever. After a lot of sleuthing I found one source which said the grapefruit juice could interfere with B12. Sure enough, I stopped the grapefruit juice, increased my B12 for several days or a week, and my energy came back. So I think it's worth experimenting with but you have to be on the lookout for this reaction.