Build a database of eBay items which includes all sales prices, time it took to sell at that price, avg. sale price, avg. time to sale

Build a database of all PAL Nintendo 64 games sold on eBay (Australia) in the last 12 months. For each game, I require the price the game was sold at (including shipping), how long it took to sell, and the date on which it was listed. Within each category of game, it can come in two forms, as either A: just the cartridge B: CIB (complete in box) containing both the box, instructions/handbook and cartridge. There are just under 200 PAL N64 games so this will mean there will be about 392 categories to fill out. Additionally, simple key word searches do not contain just the item of interest and thus a method for removing false positive in these results should be employed. From this data, a dot-plot should be created with a line of best fit. From this dot-plot, a function should be derived that gives output y, when costs total x percentage of average sale price, where y is the optimal price to list this item at to maximise profit/time (assuming that increased time to sale doesn't increase costs)