I like that you have been experimenting with events. That's the way to learn
Remember that you can both sell and buy in a shop.
If you do both, then it depends on what was worth most.
If you buy for exactly the same as what you sell you will have the same amount before as after and get the didn't do anything at shop branch. (i.e. you use what you have earned, not more, not less)
It's are minor stuff, but still something you have to consider