This is a stupid noon question but can someone tell me the best ways to make a lot of money in this game? I feel like I've never fully understood the AC economy.
Starter cash is usually from foraging and doing errands, don't forget to find and hit the "Bell Rock" as many times as you can each day. Duplicate identified Fossils and gemstones are a nice daily source as well.
Endgame is playing with the Stalk Market by buying Turnips on Sunday Morning, check Reese's price at Re*Tail every morning before Noon and once after. Looking to buy low, sell high here. The biggest downsides are that you need money to make money, lots of storage space required, obsessive logging in on a set schedule, they rot a week after they are purchased or if you time travel, and the game can (rarely) screw you out of profit. Usually people will let you sell in their town if they have a good offer available, but they usually ask for some of your Bells in return. There are some online tools that help predict when you should sell, like
this one, and they've never led me astray.
In the middle are two methods:
1) After 5pm, the Island is an amazing money generator. Catch big fish (release Sea Bass), sharks, and rare beetles, pop them in the shipping container and take them back to the mainland to sell. You can use the Rental Net as a tool to get rid of nearby bugs and fish you don't want so that new ones will spawn (or just chase them off your screen/into the ocean). Downsides are that you have to have iron reflexes for shark catching, be good at catching bugs, and that it can be time consuming if your spawns suck.
2) Perfect Fruit is good if you have a large, open space for many trees. It is very reliable, but time consuming (picking, basket-ing, travel time to storage facilities, replanting dead trees as needed) and needs another person with a different Native Fruit so you can travel to their town to sell yours. It is also a very slow starter and you might want to have the Golden Axe before you begin, but it is very easy to maintain once you have an orchard. These are really lazy Bells you can listen to music or audiobooks while gathering.
If you learn better through watching instructional videos rather than reading or trial and error, there are a million Bell guides on various video services.