>>715826520Mami > Madoka > Homura > Kyouko > Sayaka
Mami is very lonely so she probably would accept just so that you would keep her company. Especially in some of the PSP game routes where she gets very desperate. Obviously i'm working under the assumption that you're an average guy and not some creepy ugly bastard.
Madoka is probably just too nice to say no. If anything she would have a hard time believing someone cares about her that way and would be happy about it. However, if you're ill intended, Homura will not let it happen. On the other hand, if you're sincere and want Madoka's good, she will actually be on your side.
Homura is actually very easy IF you sincerely care about her. She was suffering from loneliness too at the beginning, until she met Madoka. If you're as nice to her as Madoka was you can gert her to care about you a lot at the very least. And since opposite sex relationships don't work like same sex ones, it would probably manifest with a romantic element. If you're going for her after she met Madoka, then if you assist her in her mission to save Madoka it's probably the best way to approach her.
Kyouko seems easy on paper since she's homeless. However, she's also a christian. It's very possible that she might outright refuse sex before marriage. She might be the easiest one to go on a date with (just tell her she can stay at your house and you'll provide food for her and stuff, she won't refuse you after that), but when it comes to sex specifically i may get surprisingly hard.
Sayaka is the closest to an average girl in the series, and what she suffers to is specifically her love for another boy. Obviously if you're Kyosuke it will be very easy, but if you're anyone else, she's the hardest because you will need to get her to move on from Kyosuke first, and even the staff seems to believe that won't be easy for her to do.