Depends on how short on cash you are and how long you will be short on cash. If you're trying to make your own organic feed, bird seed wont cut it. If it were me, I would purchase the cheapest non-organic layer pellets. Then, I would supplement with healthy treats. You could sustain that cheap approach indefinitely because their primary ration is still a commercial ration.
If you are set on making your own feed, don't use more than 10-15% flax. For that matter, I probably would limit everything to that percent. You will also need some calcium which can be crushed egg shells, oyster shells or limestone offered free choice. I think your biggest challenge will be achieving the right level of quality protein while maintaing the right levels of vitamins and minerals. The best way to ensure that is variety. Meat, fish, nuts, and nut-like seeds (sunflower, safflower, flax,etc.) should be your sources of protein. Corn, wheat or oats can be your filler. Fresh veggies and othr greens should be your treats. The more diversity, the better.