Hello there and welcome to the game and these forums!
- here are a couple of simple video introductions:
Here is a generic welcome video from a few years back, still very good:
This from a couple of friends (they are really keen on Dawn… try not to get influenced by this, all the nations are awesome).
If you want immersion, LARP isn’t a hobby that lends itself well to film… photo montages with thundering soundtracks, yes 
(watch out there are LOADS here… recent Empire ones at the top)
https://www.youtube.com/user/F1LTH1980/videos
- Your best starting point, i think, is to choose some sort of starting concept and pick a nation to play it in, or pick a nation and choose what to play in it.
A good starting point is to read the top page of each nation, see which one or two appeal to you, then look a little deeper.
What experience do have have at LARP/Camping/Role-playing games, if any? (None at all is fine).
As noted, there are no starter nations etc, and there will be new players in every nation. There are a few more complex areas of the game I would not reccomend for your first event, but that’s an issue for later.
- Well that depends. You CAN all do the same sort of thing, in the same group, in the same nation. This will give you a powerful but rather focussed view of the game (for instance, if you’re all playing ritual magicians you may entirely miss things like the trading, or military, or political, or religeous games… which may be fine or not.
I would suggest you (plural) look at the sort of things that interest you, and each pick characters based on that. And then either form your own small group (3 is fine, there are groups of 20+ but also many of less than 5) or all join the same one.
This would give you the incentive to head out and explore things individually, and a place/reason for you all to meet up and play together.
Happy to discuss this further, and answer any questions. 