What are regular catalysts worth? I have a strawberry fields faelora, a blue morpho morkko and a blazing sunset qitari that I want to sell but I don't how much to ask for. Also, how do you trade other players?

There are trade buttons on your sculpting page. One for supplies and one for catalysts. Simply click the item you wish to trade and then hit the appropriate trade button. These trade buttons only allow you to send the item to another player. If you wish to receive money from the player you'll need to send any random cheap item you don't want to them with a CoD. Players often use mushrooms to do this since they're super common and virtually useless.

At this stage of fest the regular catalysts like the ones you have can be very hard to sell since by now most people have the catalysts they want. You'll probably be looking at 5k max for each if you're lucky.

Oh, I meant how to trade things like avatar items. Thanks for telling me about the catalysts though.

The small envelope icon underneath your inventory is the 'mail to another player' button.