It all comes down to personal taste really and if it were to easy though, you won't have much to do in terms of designed gameplay.

Troll battles are good for experience when you know what to do though Using level 1 girls and maintaining low stats (takes a bit of fiddling to find the perfect blend for each troll) will net you a good amount of exp due to the number of orgasms you get within the battle.

Mojo is a concern I've read multiple times already but remember that PvP doesn't bring anything more than the ranking itself. Moreover, if you want to reach the high rankings, you should refrain from hunting girls at all because of the energy lost doing so.