I am at 14th now so I can't really comment on what is beyond. I will try to
give some good advice for getting to where I am and for doing well once you
get here.

One thing I strongly recommend is travel. I started in Felwithe (being a
high elf) and faught around there up to 5th level or so, then I moved on to
the orcs of crushbone for a couple levels (up to about 8th I think). At
that time I went to Butcherblock where I found lots of good stuff to hunt
including goblins, scarabs, drakes, and undead skeletons (at the
chessboard). Most or all of this time (levels 6 through 10) I was in a
small group of 2 to 4 people. At this point I felt ready to travel a bit
and went to the continent of antonica.

There I started fighting in the North desert of Ro (again in a group) for
good money and xp. We could fight desert scarabs, tarantulas, madmen, and
dervishes. I leveled up till 12th or 13th level here when I decided to head
west. I went from Freeport all the way to Qeynos on the west side of
Antonica and then across to Erudin on the western island of Odus. While
travelling I stopped in as many places as I could find. I went to the
dungeons of Befallen (off west commons), Splitpaw (off of S. Karana), and
Blackburrow (off Qeynos hills) and did as much adventuring as possible in
each.

The key to travelling is 12th level I feel, because at that point you can
bind yourself along your journey. The point of travelling is to get a feel
for the lands. I discovered lots of new zones and areas to fight (and earn
money) that I would not have had a knowledge of unless I travelled (and
reading spoiler sites barely scratches the surface of what you will find in
areas, trust me).

I leveled up to 14th in blackburrow and then went with a newly met friend
back east to the beholder maze. This area is really cool yet dangerous. I
will go back there around 16th level when I can fight more effectively
against the higher level beasts there.

Now still at level 14 (close to 15th) I made my way back to freeport and am
currently fighting caimans in oasis (solo for the first time in a while) and
am doing really well. I had tried soloing these caimans at level 12 and 13
and I just barely couldnt do it. But now at level 14 I can root (which is
holding surprisingly well) and have enough mana to kill a caiman (which con
blue by the way) and still have about 20% mana left when done. One time I
encountered a pretty nasty one that seemed to have high resistance against
my spells (did 2 damage and 4 damage instead of 80). I had to get a little
help to finish this one off, but that was the only one I really had a
problem with. Soloing caimans and resting I can earn about a bubble of xp
per hour (not much loot but good xp) which is pretty good I feel.

So If you are wondering why you cant solo very well at level 8 or 9 or 10,
its because we just cant. Root is way too unreliable usually, and we just
dont have the mana to cast it 2 or 3 times that might be needed to get a
good hold. We dont have enough hp to take the damage while getting root
off, and we dont have enough mana left to kill the beast after rooting.
Trust me by about level 14th this will all get better. I can now solo very
effectively I feel and will probably level up to 16th very quickly and by
myself. After grouping from levels 5 to 14, I am ready for a little solo
play.

Anyway, this has been really long, but the basic fact is that you have to
play in a group most of the time. Travel a lot and you will find areas that
are solo viable and new ways to make good money. Through my travels I didnt
earn much xp but put about 40 plat in the bank in just a few days of play
(not bad for level 13). Find a good group and enjoy group play, but know
that you will be able to solo if you take the time to explore new areas.

-Solric of the 4th circle