Once your max has reached 10-15mil you'll probably want to start seeking out other areas to gain in. You can of course stick to Ginyu Base all the way from the beginning to 100m but there are some other options now.
Don't forget to stop by Sonata to learn Zanzoken from the quest. This quest starts in a bar in the northwest of the area. Check the Zanzoken section for details.
Also on Sonata you can learn Kitransfer and Kiheal pretty easily from a quest. Check out the Sonata Shrines section for that.
You'll probably lose your Proof of Body and Soul if you still had it around 10m base. It automatically drops.
You can get another infinite light from killing Nappa in the Ginyu Base, he is usually wandering around the second level of the base. You can also pick up a star fragment from Vessen. This is a VERY high PL area so you'll have to be very careful finding the shop, which is to the north and northwest and hidden behind some junk (PUSH JUNK) and will cost you 500,000. You can also buy an oxygen tank here for 750,000.
You might want to consider doing the quests for Meteor Strike and Bodyslam now as well.
Visit the Hydia Temple for some nice EQ you can wear around 25mil base.
Lotus temple, has mobs starting at 10mil, and increasing to 20m, 40m, 60m and 80m. There is also a really great quest for some items if you don't have any rings, amulets, or wrist and ankle gear. They have +gains and decent stats. The Ankhs even have a slight healing buff for you. You can get here by IT'ing to Mhenlo and heading north. Mhenlo also starts the quest and mentions it when you enter the room. Check out the quests sections for that quest.
Majin Wasteland is another area that starts at 10 million and goes up to 500 million. You can get here by IT'ing to Mayhem or by traveling to the west end of Torture Street and then going northwest. The first mobs you come across are too high level for you now but if you travel out into the west you'll find some to fight. You can also complete a cool quest to get Bodyslam and Meteor Strike! Check out those sections for more info. This might be my new favorite area for this range. Just need to be careful that you target the correct mob because they wander around together. There's plenty of healing rooms scattered about, just pay attention to the room descriptions, they are usually small rooms off to the side.
In West City you can find some mobs to fight in the Warlords Domain in the southwest section, starting around 20 million. There are also some Xaolin Acolytes that you can find when you're heading north out of the City. There is a secret exit 6 to the north and northeast of the intersection of Capsule Blvd and Template street before you get to Korin's Tower. Inside the temple use the STAIRS command to go up through the "somewhere" exits. You can IT to Matt to get to West City, or walk west after leaving the Capsule Corp. Neither of these are particularly good places to gain though.
You can find some things within the Hydian Rebel Base as well. You have to work your way in pretty far before you find anything worth fighting in the 10mil+ range but it can be worth checking out if you're bored. It is an old area however and it shows. You can find this within Hydia City, or IT to Lisa, s, w, w, n, n, open down, down.
This area has a bunch of mobs spread out throughout the area going up to 100m. Further north there are even stronger mobs well into the billions and trillions so be careful. The respawns in this area can be a bit weird because of the day and night cycle but there are plenty of areas to heal and a bunch of things to kill. IT point is Kaspen or Sherpa.