Take note that ukuleles are not always cheap. There are some expensive ones that are truly worth your money because they can create a great sound that will allow you to play with ease. When you buy cheap ukuleles, you can already expect some issues, the intonation will not be that good.
You also have to tune the ukuleles properly because there is a big chance that they will not sound good. If you have a tight budget, you may want to save up just a bit more for a ukulele that will allow you to play better. The ukuleles that you can buy for up to $20 are probably just toys and cannot be played to their full capacity.