Hey Throow,
Possibilities to expand your bag space depends on the Server you are playing on.
If you're playing on
free2play (Evolution) you only get a certain amount of Space upgrades for free, after that you have to buy more space with Expansion Tokens.
You can easily find them via the Plus symbol in the bottem right of your Bag.
Also you can get them from your daily Gift (Not a day without a Gift), buy them cheaper with Premium Levels or get them from the Fair or the Free Traders.
The bigger your bag, the more Expansion Tokens you will need.
If you're playing on
pay2play (Smuggler's Paradise) you can expand your bag a little bit with Gold at the NPC in the Bank of your Fraction up to 30 Slots.
(NPC on League Side)
After that you will be able to increase the capacity of your Bag through Raids. The first raid will become available at level 45 and allows you to recieve a bag with 42 Slots. The biggest Raid Bag is, like Dragagon said, the one from the Eclipse Raid (Level 55) with 54 Slots.
The next option is to participate in special Events via the Forum, Facebook, etc. to get
Marks of Accomplishments, which will allow you to buy even bigger Bags with up to 78 Slots.
I hope I could help you, if you have more questions just let us know.
Best regards,
Poloo
Allods Online Moderator Team