I'm trying to optimize the money I can make each season, so I can spend the late game mining, fishing, and other fun things there are to do in the valley!
What crops provide the most daily profit?
By daily profit, I mean profit per day it needs to grow.
Edit: Accepted Timmy Jim answer because exactly answer the question, but you might want to look out Mage Xy's. The tools he proposed are really nice.
Following this guide, the following crops provide the most daily profit:
Spring
Summer
Fall
Note that each dollar amount is by a per crop basis. So 10 pumpkins would bring in $169 in one day. This is also strictly based off of crops alone and the base quality of them. Higher quality items will increase the amount per day.
This depends largely on how intense you want to get. Do you want a full, number crunched answer? There are lots of tools out there that you can use to calculate your profits based on starting resources. This one is pretty popular, as it shows results in a graph and allows you to specify how much space and money you're willing to invest. There's also the one I use, which shows what crops to plant on what day in order to get the most out of your current resources.
However, if you're just looking for a simple, no-thinking-required answer, the best crops to get per season are as follows (based purely on a profit/day or profit/month value, which is not always the best measure of investment):
Spring: Strawberries provide the best profit per month if you can plant it at the start of the month, but Rhubarb (purchased from the Oasis in the desert) and Cauliflower are the best profit per day.
Summer: Blueberries are absolutely the best crop to plant, having the best profit per month and per day. Starfruit is second best, with Red Cabbage trailing not too far behind.
Fall: Rare Seeds (bought from the Traveling merchant) provide a massive profit (both per month and per day), but chances are you don't have many of them since they are hard to come by - even harder than ancient fruit. Cranberries are also extremely good on a per month basis. In third place is Yams or Artichokes.
Winter: You can't grow anything in winter other than the winter forage seeds, so the choice is pretty easy here, don't you think? :)
In my opinion, if you have enough seeds and a greenhouse, the absolute best profit maker is the ancient fruit seeds. They take a while to collect, but with a seed maker you can quickly fill your entire greenhouse. Combine with a large keg setup (in your shed preferably, though anywhere works), and you can easily make a huge fortune, though it might take a little time.
If you go to the crop section of the wiki you will see a list of every single crop you can grow (some cannot be grown until later in the game as Pierre does not initially sell them). It will list what it sells for, at no star, silver and gold stars, and then below that the gold value/day.
If you have access to other things such as preserve jars and kegs, it changes the value of some crops.
In general:
Spring the most valuable crop/day is Strawberries, so save money and buy a bulk at the Spring Egg Festival.
Summer is blueberries, they regrow every 4 days.
Fall are cranberries, but they are every 5 days.
There is also this spreadsheet that details the per day value as well as the per month value. Their stat shows melon as a higher per day value than blueberries, but blueberries being better for the month. They also show pumpkins as better per day, but cranberries as better for the month. (Long term value of multi-harvest crops).
NOTE: All crops can have skewed numbers based on a variety of things (which can make melons vs blueberries close per day worth for example). Fertilizer usage (do you get gold or no stars) and the numbers of berries dropped per crop are the two biggest factors.
