Converting Tokens to crystals

Credits are currently used for Multiple reasons:

1. You can use them for self revive out in the field

2. They can remove modules from sockets in items

3. They are used in the Player Marketplace for equipment and other items.

4. You can exchange them for RedBeans in a player driven economy (you set buying/selling prices)

5. Arcporting (fast travel) between SIN towers in Accord control

Converting all of your Crystite to credits is probably a bad idea as Crystite is still a main component in research/crafting, repairs, and purchasing goods from NPCs.

Source and more information here

Due to the free VIP status that they gave as a reward for the chosen invasion, I've been able to confirm that VIP gives you +8 (to a total of 16) slots for market transactions.

I'm not aware of any other way to raise the limit.