Since you are/where 44 dranik's scar is a nice place, i soloed the first cave only more or less during a weekend(roughly 8 hours hours a day)
and leveled from 47 to 51, got some +4 augments and made a bit of money, most things dropping in those caves sell for 10ish pp, batwings sell for like
30+ pp for instance.
Soloing realy shines when you get spirit of puma at 50, self buffed except for kei i could take 3 mobs at once and live thanks to puma, i'm sure my dot duration and dmg focus helps some to
Marus seru is not a bad place but rather empty on ab most of the times, the nasty part with hoppers are there hp regen, miss a few times and there hp goes up, sucks for a low dps class like my cleric, but good for skill ups since you stand around hitting the damn thing for a long time
---Edit
Not using any ds potion mysellf even though i can make them, rarely use haste either since it takes a lot of mana to keep me and dog dog hasted and the duration is crap, getting the pop armor piece with swift like the wind if i can only find the items needed.
My gear is also somewhat twinked so i guess that helps soloing