I'm still playing 1.5 so I'm not familiar with the new crops yet.
The best profit crop for spring, summer, and fall is probably ancient fruit. You only need one seed to start, and then use the seedmaker. The plants keep producing their valuable fruit through all three seasons. Permanently in the greenhouse and ginger island.
Early in the game, for outdoor crops, your best bet are the bigs (cauliflower, melon, pumpkin) or berries (strawberries, blueberries, cranberries). Once you fix the bus, rhubarb in spring, star fruit in summer.
Some players don't bother with winter crops, but I do wild seeds. You can dig to find winter roots (I dig the beach and by Robin's) which give seeds in the seed maker. Or the crafting recipe to make the seeds.
Of course, biggest profit is not always really the best. Certain crops are needed for recipes, and I often grow loved gifts when I'm building friendship. Wheat isn't a good money maker, but grows two seasons, and yields hay when harvested. You can even just let the rain water it, it only needs 4 rainy days to finish growing. Coffee beans aren't worth much money, but the speed boost is great!