There are several instruments that you can learn to play as a beginner. I am sharing the major ones here:
Piano - Either you are an adult or a kid, it is easy to learn playing piano or keyboard. Your concepts should be clear, and reading the music sheet is going to help you a lot in learning and understanding this musical instrument.
Guitar - If you want to learn to play a bit challenging but trendy musical instrument, you can pick guitar. As a beginner, you should start from Yamaha APXT2 or other these
happynewguitarday.com kinds of 3/4 acoustic guitar because they are not inexpensive but also easy to carry for novices. Especially if you are a teen, the selection of a 3/4 acoustic guitar is a wonderful option. Adults can also start learning guitar from a nylon string guitar, and then you can switch to the steel strings later.
Ukulele: It is another easy to learn and handle musical instrument that I think adults should pick. This instrument is also affordable, and you also don't need any further maintenance. Even you can get help from online video tutorials to play it.
More instruments that you can play could be Harmonica, Drums and Bongos etc.
There are no shortcuts in Life.