Eugene's observations

Cleaning the printer maintains the quality and resolves problems.  The most common issue is white lines or the wrong colour and a partially blocked nozzle in the print head will cause both of those.  The first step must be the printer's own inbuilt (in firmware) cleaning cycle; try this a couple of times but no more as if the dried ink and paper dust are too solidly baked on more ink will just exacerbate the problem.

The next/other step would be to get some isopropyl alcohol based cleaning solution, kitchen towels, a syringe, a torch, and a pair of Marigolds.  The problem will be in the print head most likely - this is built into the cartridge housing in cheap printers, a separate fixed component in moderate printers, and detachable in the expensive ones.  If you can detach the print head then soaking it in a bath of the cleaning fluid would be the easy way to proceed.  For a fixed print head try moving the head to the centre of the platen and place a folded kitchen towel underneath.  Now inject 2ml of fluid up the pipes and leave it to soak for 15 minutes.  Putting the cleaning fluid container in a glass of hot water first will help this work its magic.  

There is a cheat?s way to avoid the time and trouble: Refillable Cleaning Cartridges.  Replace the ink cartridges with them, ?print? a few pages, replace the ink, Bob?s your uncle.

Maintaining.  Simples, just make sure you print at least a page every three days and never let the ink run dry.  Run the light cleaning cycle when you do your computer housekeeping every few months.  Also remember to power off using the switch rather than simply cutting the power.  

Buying.  Yes you can buy a new printer for £30 but not only will you not be able to maintaining it to prolong its life, but you will probably have all colour inks in one cartridge, so when the first runs out you have to throw the rest away.  This rather leads into the other and main issue:  the cost of a printer is more than the initial purchase price, it's the running costs that accumulate over its lifetime too.  So cost of ink and efficiency of printing are significant factors.  In a recent comparison between several common printers from different manufacturers PC Pro magazine found that whereas the cost of an HP Envy 7640 was £138 new, after factoring in a lifetime's printing - they used a figure of 7,500 pages - the lifetime cost was £501.   In comparison an Epson ET-2600 costing £224 new had, after printing 7,500 pages, a lifetime cost of just £229.

Bonus tidbit.  Printing wirelessly is convenient but slow.  Using a USB cable is relatively fast but to print from your tablet you need to print via the computer.  More expensive (circa £120) printers are networked using an Ethernet connection to the router to give you the best of both worlds.  But if one method fails don't think you can/should just switch to another - cheaper printers can't handle multiple concurrent connections; in case of failure an uninstall/reinstall is the solution.