After the newbie areas...
At 1 million base powerlevel the Halo light that you get from the tutorial will automatically remove itself. If you did the quest in icerian proving grounds you can use the proof as a permanent light. Your z-shard will also stop working so you'll want to consider replacing it with the Eternal Dragon Statue, you can find that quest in the "Where next?" section or quests. You also won't be able to use the newbie capsules anymore, head to the INSTANT TRANSMISSION section of the website to learn more about that.
Sonata Mountains / City / Temple
Samurai's around the streets are 1mil, then head north inside the Temple to fight mobs starting at 1.5mil. There are mobs of 2m, 2.5m, 3m, 3.5m, 4m, and 4.5m.
Make sure you are flying around the northern area, there is a pond you can fall into and get hurt and then drown. You can go all up to rest and save yourself until you can fly again if you do fall in.
If you can breathe in water (or find a way to) the Monks here mention the Koi drop a very lucky item.
The Ginyu Base
This area always has options from 100 up to 100 million. The gaps are a bit larger than some areas. 1m, 2m, 4m, 8m, 10m, etc. Explore each floor and go around in a circle. Some of the mobs here will drop some pretty decent gear. The saibamen stuff is ok, but seems too rare to matter, and the other warriors have some decent drops on the second floor. The stuff from Lorren in bear forest is better, but much more expensive, these drops are free.
1m elite warriors drop - Spiked Combat Shoulderplates, 500 armor, 6 str, 6 spr arms gear no layer.
800k captains drop - Hardened Combat Boots, 300 armor, 6 spd, 4 frt, feet gear no layer.
200k cadets drop - A Hardened Combat Chestplate, 1000 armor, body 4 str, 4 frt, body no layer.
600k drop Hardened Combat Kneeplates - 1000 armor, legs, 4 str, 6 spd
400k drop Hardened Combat Gauntlets
Tree of Might
This area is located in the very south eastern section of Capsule Corp on earth. SAY YES to the guy and you'll get transported in. SAY TERMINATE at a small brown box to exit the area.
There's warriors at 1m. ENTER the tree and go UP to find 5m warriors to fight. The 5m warriors have a chance to transform into 7.5m warriors. These enemies seem to be a bit tougher than average but it is an alternative if you want a chance at gem drops.