There's a tendency to put off buying paper and ink cartridges until you absolutely need them. That might mean a late night run to an office supply store to buy a single magenta cartridge or a fresh ream of paper so you can finish an important presentation. And that also means spending a lot more money.
Individual ink cartridges, particularly at brick-and-mortar office stores, often have a high markup. Even when you buy online, single cartridges tend to be comparatively expensive. Paper is the same. If you buy the small packages often aimed at consumers, your cost per page is higher than if you stock up.
Consider buying multi-packs online. Just like almost any other product you purchase in bulk, there are some pretty significant savings to be had. Multi-packs of ink typically include every color you need to keep your printer running, and they're often several dollars less per cartridge, meaning you might save $10 or more. You can purchase an entire case of inkjet paper for a substantial discount over what you'd pay for single reams. Buying paper from an office supply store rather than a general retail store will generally get you more pages for your dollar as well.
Rather than buying a stack of printer cartridges all in one go, you can also get a bargain by subscribing to an ink replacement service. You'll get regularly scheduled deliveries of replacement ink, often for a lower cost than if you bought those same cartridges one at a time in a store. Newer, Internet-connected printers may even have this as a factory-installed option. You subscribe to the service, and then your printer orders its own ink automatically when it's running low. Bonus: You get all the perks of buying in bulk, without having stacks of cartridges lying around.
Not only are you stocking up and saving money, but you'll have fewer panicked trips to the store, too.