I've had this one from Amazon for a couple of years now: https://www.amazon.com/dp/B00NOAKUBM/ref=cm_sw_r_cp_api_wF-sAbRFXH5GZ

I like that it is sleek and you can choose to have the light portion off of you want. It'll also run through the whole night if you fill the tank to the max, which makes it a good option if you plan to use it while sleeping. I always recommend it to people when they ask because we have loved it the whole time we've had it!

Best things to look for in a diffuser in my opinion are timer settings (how long do you want/need it to run for, how many options are there), light settings (a lot of them come with color options which I hate but other people love), and overall look. Hope that helps!! :)