I ask people to leave reviews after about 2 weeks after I ship out (gives them plenty of time to receive and try out the item. Also it’s a good way make sure that the buyer has actually gotten their package) and usually about 1/3 of them are more than happy to do so after a reminder. Its not everyone but it does make a difference. My reviews to sales ratio is about 3:4. Just make sure it’s a “no pressure” type of reminder. Absolutely don’t beg for a 5* review...just tell them something like that their feedback is valuable to you. And if they don’t reply or leave a review just move on, there will always be others.

Also I wouldn’t worry too much about the ratio. It’s the quality of the reviews that really matters at the end of the day. I’d rather purchase from a seller with 200 stellar reviews than a person with 2k reviews and half of them are 3*