I'm not sure how to reply to this without being reduced to one of those aforementioned peoples.
Definitely reducing transfats, saturated fats and cholesterol will improve circulation and decreases blood pressure. These things absolutely 100% affect your mood and cognitive abilities. Of course though, it's not magic.
As Jazzy said, cutting caffeine is so important. At my worst I actually quit caffeine all together for a couple years, and I felt like a completely different person. That's purely anecdotal evidence, but it is something lots of people talk about.
Also, avoid self-medicating with energy drinks, tobacco, alcohol, and also over the counter medication. It may seem obvious, but taking heaps of antacids for stomach issues related to C-PTSD is a bad idea, trust me on that. There are long-term consequences.
Making sure you're getting enough vitamin D and omega 3s. I know you said you can't do expensive supplements and I don't know where you're from and the cost of nuts can be really expensive, but if you live somewhere where walnuts are affordable, eat some regularly to make sure you meet your omega 3 needs without combining it with cholesterol and heavy metals which have a paradoxical effect on the brain. You said you can access to an Asian grocery store, edamame is also a good source of omegas. Just don't salt them too much as salt increases blood pressure which increases anxiety.
This is probably the most important advice I can give. Lots of people with trauma disorders try to have absolute control over their health through their diet, exercise and other radical lifestyle changes, and it can get really unhealthy. Sometimes we try to take control because we never felt we had control, or because it's a way the inner critic tells us it's our fault and that something should be fixed, and then self-blame sets in. This makes it a very slippery slope. Of course it's important to be conscious of our habits and to exercise self-improvement and it's equally as important to really understand why it is that we're wanting to make those changes and have a grounded expectation of our results. Those with C-PTSD are especially vulnerable to eating disorders of all kinds as well as the health implications of using food as an emotional tool.
No matter what anyone says about curing their trauma disorder through lifestyle changes alone, it simply does not work like that.
All in all - Have a real conversation with yourself about your motivation, and then when you REALLY know what it is you're trying to fix research that specific thing, manage your expectations of results, make healthier choices gradually, at a pace that feels comfortable for you. This not only is healthier, but will make your changes more sustainable long-term instead of bandaging the issue.
Minimize cholesterol and table salt as much as possible, get enough sunlight, eat nuts and seeds, try to move your body but don't stress about it, you shouldn't self-medicate, be compassionate to yourself and understand that set-backs are not failures, check in with yourself, your goals, and your motivations often and with honesty.
If you're not sure where to go for accurate information I highly recommend nutitionfacts.org. There are videos on a huge range of topics from how dietary cholesterol effects cognitive function, how caffeine effects cholesterol function in the brain, how to decrease salt in your diet, etc.
Oh, and honourable mentions go to sleeping, drinking water, showering and all those things. But, in the direction of self-compassion, those with PTSD have a higher rate of executive dysfunction, and the more PTSD symptoms increase, the more executive dysfunction increases. So, tackling executive dysfunction issues, or at least understanding them, may also help you to feel better.
