Well, there are a few ways to go about this.
Here are some suggestions:
1. a.) Making a clan/group?Creating your own clan or group from scratch will require a fair bit of dedication and possibly some background knowledge if you want to meet your aims.
A good way of going about it would be by firstly choosing what kind of a group you would like.
This might be a clan, gang, family or a general RP group in Argonath.
Once you have come to a decision on this, think about how you will operate and the appropriateness of this new group in the server/forums.
Come up with a name, tag as well as a recruitment process. It's best to start off with a few supporting members to help you expand at a decent rate.
Also, it's quite important to register your new group on the relevant section of the forums.
b.) Joining a clan/group?Probably the better option for those that are new to groups and/or Argonath. You can join one of the various clans or groups that exist across VC:MP.
2. Gang HQsCurrently, these are only for gangs/criminal based groups.
Start off by ensuring that you have a stable group in the server that is active and does comply within the AR rules.
Next, find a suitable property that you would like to have as a base.
Once you have got to this stage, it would be best to approach the administration and hopefully we can sort things out from there.
Note: The building/location you choose does not have to be scripted already.
3. Storing weaponsRight now you can't store weapons in general properties.
As for those that are scripted as gang HQs, there is a system that will allow you to buy in and directly store weapons.
There are some extra management scripts that come with the HQ that will allow you to set weapon lists as well as members.
Useful area to look: http://www.argonathrpg.eu/forum/index.php?board=184.0