As with all instruments, the more you play, the better you get. The best way to ensure you’ll play and improve is to PLAY THE SONGS YOU LOVE.
Here’s my list of the best ukulele books currently available. Of note, The Daily Ukulele or “Yellow Book” provides 365 playable tunes and is the songbook choice of most US based ukulele clubs. It is also available for your Kindle. Mele! Mele!
TIP: Remember to strum a little every day. It’s better to strum for 5 minutes daily, than for 1 hour weekly. Repetition over several days really locks it in!