I'm sorry, I don't have all this figured out for myself. I know I'm missing things in my diet and I did some preliminary analysis with the help of my GP and a testing lab, and I think I have a handle on the broad strokes for myself, and where I need to improve.

I'm technical, so for me the process is simply to identify the issue, and ratify the issue as best as I'm able. I've started the first part of this, I have yet to do the follow through. Unfortunately, I find myself in a bit of a difficult personal position and can't really afford to make any significant changes to my life at the moment. My long term plan is to grow a garden. I'm finally in a physical situation where that's viable (I recently moved out of an apartment, where it was very difficult to grow a garden at best, into a home with enough space to have a dedicated area for gardening outside). I want to eat as much of my own produce as I can, which will provide more fruits and vegetables than I would normally have access to, which will hopefully be good over a longer period of time. That's just to start. Better, cheaper, produce that's more easily accessed and readily available, to encourage myself to eat more leafy greens and such.

I know a garden big enough to continually do that (at least through the good seasons for growing), is a significant challenge, since it can occupy a lot of room that can't really be used for anything else. There's also nontrivial investments to be made into things like fertilizer, mulch, soil, tools, seeds, and so much more. And this is just step one for me.

I'm not in a financial position to go for it yet, and growing season is over for this year, but I'm going to save up and hopefully I can start next year.

The only reason I'm talking your ear off about it is that growing your own fruits and veggies is pretty much always a good option. Commercial growers tend to prioritize the size of the produce over everything else, so they can be paid more for what they grow. A good looking, large apple (as an example) sells better and for more money than a smaller, oddly shaped apple, even if the latter is much more nutrient-dense than the former. If you grow your own with even a modicum of research into which variety is best to grow for yourself, you're going to have better food to eat that costs less, all for a small amount of effort.

Apples are a bit tough, even if you're in a house, apples grow on trees and usually don't produce any fruit until they're a fair size; so that's probably a bad example, but the underlying point still stands. It's a good starting point, and, while difficult to do in an apartment, it's not impossible with a hydroponic type system. A small "grow" tent, with a rack and some deep plastic pans for the soil, plus some grow lights and you're good to make a small garden; but even dedicating only a few square feet to it may be a pretty significant ask depending on where you live specifically.

IDK, that's the only real thing I can contribute right now. I'm sure other commenters will have suggestions, and I'm certain there's plenty of info on the internet, just be weary of random search results, as much good information as there is online, there's also a lot of bad info trying to sell you something.

All the best.