okay next question: is all this inventory finite or infinite? that is, are there only going to be like 100 pens total in your game, and they just get moved from store to store? or is it more like : store A has pens and pencils in their inventory. when you go to store A, a random amount of pens and pencils are spawned for you to buy, and buy/sell prices are based on that randomly spawned amount?
if it is the first (100 pens total being moved around from store to store) then i suggest making the price calculations universal. or if you wanted to get even more in-depth, here's a scenario for you: let's say that there are 10,000 pens for sale and they are randomly distributed throughout all 4 of your stores. let's say that
store A has 2,000 pens
store B has 4,000 pens
store C has 3,500 pens
store D has 500 pens
so BEST case scenario would be for me to go to store B, buy some pens, and then sell them at store D, right? But I could also purchase at store C and sell at store A for a little bit of profit too. But if there are only 10,000 pens TOTAL at any given time, if one user goes and buys 500 pens then that only makes 9,500 available for you to buy and sell. this should make prices go up overall.
How you actually display everything in your game will determine a huge chunk of your game mechanics. For example, are you planning on the user being able to see prices for all the stores in some kind of quick list, or do they actually have to go from store to store to find out prices?
Having to go from store to store probably won't be very practical if you have inventory randomly spawning and therefore prices being more random. Playing would be more luck of the draw than strategy. Also you would end up having superfluous stores. For instance, if it's all random, may as well hop back and forth between shop A and B until it spawns a good (low) amount and therefore price and then sell, rather than bother with going to store C or D. Or hell, could just keep entering and exiting the same store for that matter.
You could have a finite amount of product (like 10,000 pens), show a list of current prices for each store, but not quantity available, or quantity available but not prices. Or you could have random spawns in each store and it be luck of the draw but give a clue in an overall table like putting description like "Pen sales are HOT at store B" that way even though there is luck of the draw involved people would have a clue that they can grab some pens and maybe get lucky by selling at store B or "Pencil sales are down at store A" then you would have a clue to go buy at store A cuz prices would also be down.
You have to start with what you like, you're personal "style" so to say, then find its balance of strategy and luck and challenge and overall fun. that's what gameplay mechanics is all about.
p.s. - I stopped working on my game a couple months of go. I lost the motivation to do it, mostly for lack of help. it was at [a href=\"http://www.chroniclesofwar.com\" target=\"_blank\"]http://www.chroniclesofwar.com[/a]
also, as far as forums for game mechanics, you might wanna visit the forums of other games, there are always threads where people talk about the game and what could be done better or what sucks or what new feature would be cool. just reading through posts like that might give you ideas or help you better understand what works and what doesn't.
i think that's how most people end up venturing off to make their own game, actually. at least, that's how it was for me, back in the day. I played kings of chaos, mediwar, darkthrone, and thought some of the things were cool but i thought i could do way better (i still think i can