I've got to travel back to town pretty often to sell my looted items. Will I be able to reduce these travels' frequency in the future ? Is it possible to buy or craft additional pouches to extend the inventory ?
It's not possible to make the inventory bigger, just to buy more tabs for the stash. I don't foresee any changes to this in the future.
My advice to you, since I used to be the same way, is to not pick everything up, just the things that might fetch more than a few pennies back in town. If you do pick up a gray it should probably be something that you want to upgrade with an orb.
best answer spoiler you should try and get the menagerie as early as possible and always have nets on hand
catch something then talk to the dude that appears that takes the animal then say something about the menagerie then go through portal and sell your stuff
go back through portal and you will be back where you were and you need to ask about menagerie again for portal to appear.