OK, first of all, "dozens of tries" means nothing to a parrot. It has taken me up to 5 whole years (and that means hundreds of tries) to get a bird to eat a good diet (granted that this particular bird was a CAG that had been badly abused and had come to me semi-catatonic).
I will tell you what my Jardine eats (which is the same as all the other parrots, from the budgies to the cockatoos). She gets gloop, one fruit, one veggie and one leafy green for breakfast and about two heaping tablespoons of a seed mix which has very little sunflower seeds (I mix a cockatiel mix with some striped sunflowers with a small psittacine safflower-based one) for dinner. My gloop is all cooked and has whole grains (oats, kamut, wheat, hulled barley, black japonica/red Himalayan rice -the order is descending in terms of quantities) with pulses (black lentils and small white beans) with a sprinkle of flax seed (as well as chia and sesame seed during breeding and molting seasons). This mixture constitutes 50% of the final product and the other half are cooked vegetables: broccoli, corn, peas and carrots, white hominy, butternut cubes, sweet potato, chopped green beans, blue kale, artichoke hearts (the last ingredient varies from batch to batch but I've been using artichoke hearts the most lately with Brussels sprouts, second). The fruits could be apple, orange, banana, pear, blackberries, blueberries, strawberries, cherries, mango, red papaya, grapes, kiwi, figs, pomegranate, etc. The veggies: cherry, grape or 'regular' tomato, yellow or green zucchini, red/orange/yellow/green pepper, jalapeno/habanero/Italian pepper, celery, cucumber, all kinds of pumpkins or squashes (cooked), fennel root, potatoes (cooked), corn on the cob, yucca, white sweet potato (the Spanish kind that is not as sweet), carrots, green and wax beans, sugar snaps, snow peas, beets, cauliflower (cooked), etc. The 'greens': romaine/red leaf/green leaf/boston/butter lettuce, regular/red/dinosaur kale, chicory, escarole, red/green/savoy/nappa cabbage, broccoli, broccoli-rabe, bok choy, green/rainbow/red Swiss Chard, dandelion greens, endives (not often as they are too expensive to buy for all my birds), etc. I never feed them spinach or collard/mustard/turnip greens.
BabyBoyd (her way of saying the name she was given: Baby Bird

) came to me 7 years ago eating seeds and apples (she still calls any type of fruit 'apple' and asks for them "Youwannapple?") and although she is not big on leafy greens, she does like her raw broccoli and Red Swiss chard (the red stalks are particularly sweet and juicy and all my birds love them but they can't get them more than once a week because they are high in oxalates) and loves her gloop and fruits. Today they had a spicy gloop (I alternate one day spicy and one day sweet), red globe grapes, fennel root and romaine lettuce (she went first for a couple of bites of gloop but then switched to the grapes which she loves but she will go back to the gloop to fill up). As you can see, she is a very good eater.