Three things that haven't been mentioned that I think are important for the poster to know are:
1. Porcelain tiles are "homogeneous", which means they're the same color and material all the way through the tile's thickness. Ceramic tiles have a clay "biscuit" with a pattern on top. You're never going to "wear" out that surface pattern on a ceramic tile just from normal foot traffic, but if you drop something hard on a ceramic tile and chip it, then the chip won't be the same colour as the tile's face and will be more apparant. With porcelain tiles, any such chips are less apparant because the tile is the same material all the way through the tile.
2. Ceramic wall and floor tiles (both vinyl and ceramic) and porcelain tiles will be made in batches. Each batch will be given it's own DYE LOT NUMBER. That number will be printed on the cardboard boxes that the tiles come in. Since all the tiles in a certain batch will be made with exactly the same materials under exactly the same conditions, then they should all be exactly the same colour and appearance. Consequently, if you ensure that all of the tiles you buy have the same dye lot number printed on the box, then they should all be identical in every respect.
However, tiles of the same style from different dye lots can differ slightly in color and appearance, and even though this difference will generally be small, it can be noticable if all the tiles in one area of a floor are from a different dye lot than those of the rest of the floor.
So, if you order your tiles from a tile retailer, the wholesaler he orders from will know this and will ensure that all the boxes of tiles that he fills each order with are from the same dye lot.
But, that's not the case when you buy your tiles from a home center or hardware store. Often, the home center will simply order so-and-so many boxes of such-and-such a style of tiles, and the wholesaler will use that order as an opportunity to get rid of all the small quantities of tiles from different dye lots that he has in stock.
So, if you do buy from a home center, then if you can't find enough boxes with the same dye lot number, then mix up all the tiles from the different dye lots so that if there are any variations in the color or appearance of the tiles from different dye lots, then that difference will be seen uniformly over the whole floor and not just in one area of the floor (where it'll look like a mistake).
3. My experience with ceramic WALL tiles is that manufacturers change the color and pattern on their tiles frequently, and if you buy tiles one year, there's a good chance that style will be discontinued within a year or two. So, whenever buying tiles of any sort, whether for walls or floors, it's always best to order extra tiles to keep on hand in case you need to replace any damaged tiles or whatever. It's cheap insurance against the problems that may arise if you simply can't find suitable replacements for damaged floor or wall tiles.
(for example, in my building, if a long term tenant get's to the age where they need to have grab bars in the bathroom shower, I would be reluctant to allow them to be installed if I couldn't replace the tiles that were damaged by that installation)
