Rainforest is hard. You need hundreds of workers to clean the jungle! I aborted my try with rainforest. The easiest map I had was Terra. With a big oversea landmass you can start to conquer the "old world" without fearing to reach the domination limit. Additionally you can send some scouts over to pop a lot of late game huts (especially for Astronomy).
As opponents I won't choose protective ones (like Charlemagne), nor the backstabbers (like Suryavaraman). If you want the huts for yourself you shouldn't choose the "hunting" civs, so no Pericles.
So my favorites for opponents are Augustus, Julius, if you are fast in conquering before they have praets, but even then you can beat them easily with cuirassiers/cavalery. De Gaulle, Elizabeth, Joao II and Victoria. All of them are non-aggressive, non-protective, no hunting, non-spirit and non-creative. From the point of an attacker, really nice attributes.
Your civ should have a trait or a UB which helps reducing the maintenance cost, so each civ with organized is ok or charlemagne (Rathaus).