I've seen people using shaker bottles on the internet and I'm wondering if they're worth the money? If you use them, do you have any recommendations?

100% worth it in my opinion. I've tried a number of different bottles over the last ~15 years and for the last few years I've been using this one which is excellent. The wire whisk ball does an amazing job of completely dispersing the powder in the liquid (every other bottle I've ever tried has inevitably left some clumps) and it's all dishwasher safe.

EDIT: First three comments in this thread all recommended the exact same bottle lol, guess you've got your answer OP!