Sit in town, and press F

To create a group, choose the options you wish from below the Create Group button, then click Create Group.

To join a group, click it once to highlight it, then click the Join Group button.

It is highly recommended that you ask if game is full, as group games are usually pre-arranged

Proficiency is not dependent upon the lvl of your weapon.
The more you use a type of weapon, the higher your prof will become
Your next prof level will not start until your char level is 1 lvl above your prof level.
So once you have obtained lvl 5 dagger proficiency, for example, you will not see a prof increase until your char is at least lvl 6

Regarding abilities (Not skills) - I recommend MultiStrike for all melee char's, even though it is designated as a Samurai ability

Sent you some fg to start

You have a friend list option in your profile where you can accept/decline specific applicants