So I'm seeing there is a difference to a collector not just the stamp itself but if it either came from a strip or a sheet. Which one is more valuable to a collector? Since I'm asking all these questions, can you point me to a link that explains what collectors are looking for? Thanks
Every collector will be interested in something different. Financial value isn't likely to be what primarily motivates them. This is just as well, as the vast majority of stamps are common and worth pennies, whether they come from sheets, coils or booklets. In terms of a rough guide, unused stamps from the nineteenth century will carry more value, as fewer will have survived. Similarly, the higher value stamps from sets, which few people probably bought at the time they were issued, because who could afford to buy and keep a £1 stamp in 1930, or who was likely to receive one on a parcel?
In terms of your box of material from a neighbour, the "value" is likely to be in the interest you or someone else can draw from them. The cash value is likely to be minimal.