(Sorry for any spelling/grammar errors...I'm currently on mobile)
What dani (daenerys) look do you want to go for? Because her look drastically changes from season to season. I recommend compiling images of some of her looks you like and deciding from there...
A huge part of Dani's look is her hair and it varies from season to season. Find the look you like the best, find the episode(s) where she wears that look and really study her hair...I recommend looking for a wig shop that provides a variety of options...ArdaWigs.com comes to mind. Start with a long, white, and curly wig and go from there. Braids ares super important for dani so either find a wig that is compatible with a variety of braids or get clip in braids...if you're not someone who is really into hairstyling or wigs I highly recommend just doing a basic google searc of dani wigs, you will find plenty of Dani wig options out there
As for her breasts, if you have a leaner frame go for a b or c cup, if you have an average or larger frame go for a c or d cup or more the larger you are
To answer your question about lingerie, look into shape wear! Waist slimmers, specialty bras, spanx, corsets, etc. They will help make your figure look more feminine and are common thing women wear. With a bit of research you may find something that's is suitable for men who want to crossdress...Now! If you want to wear lingerie for sexy reasons, yes! No one may be able to see it, lingerie is great and can be a great confidence boost!
This may help you pick out a look: https://www.google.com/amp/s/www.hig.../%3Fformat=amp