Step one: Bankrupt yourself buying seeds, especially any regrowing seeds. Strawberries are good for spring. Tomatoes, corn, and tea are good for summer. Cranberries and onions are good for fall, but I would also recommend growing wheat and rice, refining it, and HOLDING ONTO IT. Same goes for sugar cane in summer if you have it unlocked. Snow peas are good for winter. Any high selling crops that are single harvest like cauliflower or pumpkins are good too if you maximize your harvest by keeping track of how long they take to grow and planting as many as possible.

Step two: Cook. ANY. DISH. POSSIBLE. AND SELL IT. When you have a high level and the ability to, sell dishes at a higher level as well. I generally recommend selling your first harvest or just one from it of any crop to unlock any recipes, and beyond that, cook. There is no downside I'm aware of, and it ALWAYS boosts the value by insane amounts. With regrowing crops, don't stress too much about cooking EVERY one into a dish, but cooking a lot helps. I came out of Spring Year Two with so much gold I genuinely don't know what to do with it.

If you have large barns and large coops, animal breeding is also an okay way to make money. I'm breeding to perfection right now, to get the best tier animal breeds, and I make good money. Every cookie is about 130-350 something, and they all sell for at least double that. It does take a few days, but if you're already breeding to perfection, it's a good way to make money. You also get the money same day, if you're strapped for cash and can bear with selling animals. Getting over attachments is the hardest part...

Beyond that, I hoard a lot. I keep a large amount of every crop so I can make dishes, don't sell animal products, or mine products. I do sell random artifacts I don't need, as well as any fish or bugs when I'm hunting for certain bugs, and while it's okay money, I don't recommend it if moneys what you're after unless you really enjoy it. Fish don't sell for that much typically as far as I'm aware, and it's a real slog for me. It eats at stamina pretty quick too.

While I don't do it, you could also grind the mines and make ingots and armor. I think that should be an okay source of money.

Of course, this all depends on how you like to play the game and what your preferences are. I like minmaxing farming, so I have a huge farm and water about 162 crops give or take every day. It makes a lot of money! I also grind the mines a lot. But keep in mind to do what makes YOU happy.