Ukulele is a great first string instrument to learn! Since it only has four strings, it is much easier to play than the guitar and suitable for all learners, including those with smaller hands. Ukuleles also have a very beautiful melodic sound and you can learn to play melodies on it fairly quickly.
It is good to start your learning journey with a good teacher who can explain the basics to you clearly. I would recommend following Bernadette Teacher Music on Youtube and completing her 30 day beginner uke challenge. She is a great music teacher who has uploaded hundreds of videos on her channel:
It is also worth investing money into a proper musical instrument. The Kala brand sells very reasonable priced soprano ukuleles that are great for beginners. They cost around £50 in the UK, brand new and ready to be played!
Finally, we would recommend getting a comprehensive beginner book to help you on your learning journey. The Hal Leonard Ukulele Method book is a great place to start.