ibril

New avatar today. I finally got it, I was starting to hate game avatars

There are options through item training, and you can read about that at the Battlepedia's Item Training Guide. The items tend to be more expensive than codestones, though, so it's not the most cost-effective way to train. 
You could also try training via the lab ray, but only if you don't care about your pet's color or species. The lab ray tends to make HP increase a lot, because it never takes away HP. It also tends to make strength increase and defense to decrease. You can always tell a lab-trained pet by their high HP and low defense. It also typically precludes you from training at the training schools, because it's tough to keep your level up with your HP, so lab-trained pets typically aren't trainable until level is significantly increased.
 
Other more unreliable options include faerie quests, kitchen quests, scratch cards, Deadly Dice, Turmaculus, Coltzans Shrine, and the Wheel of Extravagance. Faerie quests raise a stat (depending on the faerie) for your active pet, but the only way to guarantee you'll receive a faerie quest is by using a Faerie Quest Fortune Cookie, which you can buy with NeoCash. Kitchen quests are a favorite of a lot of battlers, but they increase a stat of a random pet, so there is no guarantee it will help out your battle pet unless you only have one pet on your account. The other options are all very unreliable because there is only a chance that your stats will be raised. A lot of other outcomes do not have anything to do with stats.
 
For more information on training, including the other options for training, check out the Battlepedia's Fast Training Guide.
 
The most reliable, most cost-effective way to train is the training schools. If you don't want to pay for it with the current prices, you could wait for codestones to deflate. I'm anticipating prices will drop when the Obelisk War prize shop comes out.

It annoys me that stamps can't be removed from your stamp album! I'd like to unstick and sell my whole first row of Tyrannia stamps. Of course stamps wouldn't be worth as much as they are if they could be removed.