I haven't played through much of the story (up to fearina's shrine), but I only have the outfit I'm wearing. Where can I gat nice clothes for my avatar?

Right now they are selling avatar sets for diamonds, with a discount on diamonds. You can also get avatar items for gold in the player trades. Another option is in the item auction area of the forums.

thank you

You can also find some clothes through exploring and battling. Some enemies and bosses drop avatar items, just very rarely. There are also some merchants and shops in the different areas that do sell some clothes as well.

Otherwise, most of the avatar items usually comes from festivals. The next one will be the winter fest later this month, so you can look forward to that. Also, theres an advent calendar going on right now, that gives a free item everyday that you can collect. Usually there are some avatar items there as well. You can access that through explore > seasonal festival > advent calendar.

Also during festivals, if you participate in official forum games, there is a chance you can win exclusive avatar items.

thank you

You're welcome ^^