Capo's are great for things like changing key and eliminating difficult to play chords, for example, but they are also useful for other reasons.

For example, they can help youngsters with guitars which are slightly larger than suits their age and which they are expected to grow into. Placing a capo on, say, the third of fifth fret, has the effect of shortening the fretboard and consequently the spacing of the frets, thus making the instrument much easier to play for small hands and fingers.

Also, it is quite common for inexpensive guitars not to play in tune, particularly at the first fret. If that is the case for you, and you can't afford to have a luthier/guitar maintenance person resolve the problem, just try placing a capo at the first fret and it is likely your guitar will play more in tune. Obviously this raises all your open strings by a semitone, so if you want to keep the original tuning, for singing certain songs etc, you can retune your guitar a semitone down (Eb, Ab, Db, Gb, ...

Just a quick comment about tuning your ukulele. 

If you are tuning standard gCEA and have a giood ear for music, one of the best free online tuning aids can be found at on YouTube here: https://www.youtube.com/watch?v=7xKTKjwGCVg. If your hearing is less gifted do get yourself a tuner. There are many different ones available and they are not all expensive. Obvious suppliers are Amazon and eBay. If you have friends who also play ukulele ask them if they can recommend a make and model before committing to a particular purchase.