Yeah... even if you're bad at them, if you actually take the time to play games and submit the scores, you can make 10k a day. Shoot, Majority Rules alone gives you 3k a day and the scores are right here on the forums!
As for restocking, my suggestion is to restock something you know the prices of VERY well. Pick something with a smaller item base, or something less popular, than just "toys" or "food". That way, it's easier to remember which things you should grab when they come up in the shop.
Also, when I do my dailies, I put the decent stuff (750 NP and up) in my safety deposit box, and the cheap stuff into my shop. I price the things in my shop every other week, and I go through my SDB every other month or so and put into my shop everything I don't want to keep.
This accomplishes several things:
1. it allows the expensive things to increase in price
2. it allows you to have a full shop when people visit
3. it gives you the profits in bigger chunks at a time, and you're more likely to spend responsibly... that is...
if you get 50ish np in your shop each day from selling your daily stuff, perhaps spiking to 1-2k when you get something cool, are you really going to put the piddly things into the bank when it appears in your shop till?
if you get 2600 np out of your shop till, you're much more likely to think about what you want to do with it: save, spend, invest, etc.
4. if you can drop your valuable stuff in the SDB and forget about it, it seems amazing when you sell it: you're not sitting around going "i have 1.2mil in the bank, but really i have 1.3 mil because i have 100k in items". If you forgot about it for a while, when you sell it and you miraculously have 100k for items you didn't even know you had, it seems like free money. It's not, of course, but it's wonderfully encouraging when you're having a bad financial week