These questions might fit better under the category of "bugs". :)
Soon you will be able to train skills at vendors, for now, using any spell that requires the "Life" skill will increase it.
To equip the buckler you will need to have the "Shields" skill, if you have the skill and it still does not equip then let me know and I can take a look.
I have noticed the same issue with potions equipped to the action slots and have been working through some ideas to allow the slots to know which type of item is equipped there, as it is right now, the action is tied to the unique identifier of the item, that is why they go away when you use them.
As for talking with real players, typing into the field below the chat window broadcasts the message to everyone online. Using the icon that looks like three people will tell you what players are online.
Anything that does not look right or function the way you think it should feel free to post that under bugs. The goal is to make the game easy to play, without a steep learning curve. It probably wouldn't hurt to have a tutorial of some kind in the game though. :)