Hi @Lusiiky and welcome to the forum!
Your best bet is to have a read of The Great Big Review and Testing Guide.
To answer your questions, you should aim to have at the least 10 well written, honest reviews on LH that are of decent length (multiple paragraphs). There’s a post under the link above that tells you how to write good reviews.
You don’t have to have purchased the items from Lovehoney. If there’s something on the site you already own, even if you purchased elsewhere, you can still review it.
Hope this helps, and again, welcome! 