“I dreamt about you last night, it was hot — very hot, have you ever had a dirty dream about anyone?”
“I don’t know if this is normal, but my legs get weak every time I get a text from you.”
“Just saw something really sexy that made me think bad thoughts of you.”
“I just had the dirtiest thoughts about me and you ever. Too dirty to even talk about ~ unless of course you want to know”
 “If I were with you right now, where would you want me to kiss or touch you?”
  “What would you say if I wanted to come over and spend the entire day in bed with you?”
 “Every time I think about you, I cannot help but think of how sexy you are.”
 ” I am curious, what is the sexiest thing anyone has ever sexted to you or vice versa?”
Once you have created some build up and she is responding in a positive manner, then and only then can you up the game and start being a bit less subtle and move into some sexier messages like:
 “Sometimes when I think about you, I want to strip you naked, throw you on my bed and make love to you until the sheets are soaked and you leave scratches on my back”
Remember, sexy does not always mean you have to be vulgar.  In fact, it is less sexy at this stage in the game.   Avoid using really dirty words such as fuck or bitch until you are deep in the middle of sex and you are sure she is going to be receptive.