Something light sweet for the first time. Citrus and Magan&Danai is an absolute must.
Then stuff that has sex scenes but not too graphic like
"My Girlfriend's Ex-boyfriend " "The Third Party" and "Prism"
Then eventually the good Yuri shit like "What Does the Fox say" There are so many good Yuri's out there it sucks they don't get the same recognition as yaoi.
http://www.mangago.zone/read-manga/girl_friends/
http://www.mangago.zone/read-manga/citrus_saburo_uta/
http://www.mangago.zone/read-manga/asagao_to_kase_san/
As for Citrus a character named Mei frustrates a lot of people at first. It takes until around ch16 for her to give Yuzu a break.
What would you recommend to someone who is a yuri virgin?