For the horseback kill you can easily get your answer in the achievement guide & roadmap.
As for experience, I suggest the room with 17 small spiders in the lost city next to the Ashland. With War's Glory enhancement you can level up weapons without spending too much time.
All my played games have exactly 1000G.
1st 1000G: Batman Arkham Asylum (PC)
1st Xbox360 game: Trusty Bell Chopin no Yume / Eternal Sonata
1st Xbox One game: Child of Light
1st Xbox360 player to obtain Obsessive Compulsive (collect all loots in a single chapter) in Thief on 25/2/2014 at Trueachievements.org
Last edited by ImaginaryRuins; 08-10-2012 at 09:25 AM.