I've had a little success with Search Ads, but only when I target one or two similar items in my shop. Every time I've tried to promote more than that, it's just a waste. I also whittle down the keyword list so that my items are only showing up for super specific searches (ie, I delete words like ring because I don't want my "silver stacking rings" to come up in every search for general "ring.") The more specific you are with the parameters you set, the more effective your ads are (potentially). At least that's how it's worked for me.
It's a limited system for sure, but there are still ways to make it work for you. Also, I generally set my weekly budget at $20 and higher. I've never ever used that much a week, but it helps to have a bigger budget so you can "bid" on pricier keywords. You can always stop your ads sooner, like when you reach your actual limit.
