You really don't need a capo, honestly, save your money.
It'll only ever come in useful for one or two songs (and while you're learning you'll not use it at all).
They essentially tamp off the strings and move the 'open' position to whatever fret you put it at. Lets you play songs in a higher key/register. So rather than tune the strings up, pop on a capo and you immediately lift the tone.
I rarely use my capo although I do have a spider-capo (locks off individual strings allowing for some freaky tunings) but even that, with all the fingerstyle music I play, comes out for only a small handful of songs.
If you really must buy one, get the spring-based one that you simply clamp on (rather than the one where you wrap the stretchy fabric around the neck) as it's easier to move/remove. Nfi on brands though.