YouTube Premium is a no-brainer, although it’s a bit tough on the budget. Many apps will offer superior functionality for free (although, with dubious legality, ads and hidden fees). Here’s a lineup of such programs download YouTube video to your device.
TubeMate
A generic application with no defining characteristics. It does the job well enough. Also works with Dailymotion, Vimeo and some other services.
YouTube Go
Very minimalistic and lightweight. This one will be especially easy on the CPU - great for outdated phones.
Videoder
Sleek and efficient, this downloader offers support for a broader range of hosting websites, such as Facebook and Instagram.