First off, keep in mind that your differential is the lowest part of your truck and there is now way to raise your differential by lifting, only by putting on bigger tires. By lifting, you are able to put on bigger tires. How much you want to lift depends on how big of tires you want to run. If you wish to run a 3'' lift for instance, you can fit 33'' tires (05-10 Tacomas). You want to coordinate you lift with your tires so that 1) it doesn't look awkwardly disporportionate, and 2) when lifiting you throw off your center of gravity and bigger tires help reestablish this.
If you plan on offroading you want a suspension lift as opposed to a body lift or top plate spacer lift. You will need new coils and shocks up front and either a block or and add a leaf in the rear. You will also need longer u-bolts in the rear to fit over the beefier leaf pack. When lifting over 2 inches your suspension components are put at awkward angles and can cause premature wear and tear. It is also nearly impossible to acquire a perfect alignment after lifting because of these angles, causing your tires to wear oddly. New upper control arms are essential to fixing this.
I'm posting a great decently priced lift below as well as the ucas in a seperate link. This is about the best and cheapest suspension lift you can get for the money.
http://www.toyteclifts.com/index.php...mart&Itemid=72
http://www.toyteclifts.com/index.php...mart&Itemid=72
If you have a 4x4 model, you may also need a diff drop kit or you may have bad vibrations.