In that case, I'd recommend checking out the
Belegarth Starter Kit. Inside, you'll find a ton of resources for most aspects of Belegarth. While not exhaustive, it's a great launching pad.
For getting better with florentine, I think making a pell is the best place to begin. The only way to train your offhand is to use it in the manner you want it to perform. Slowly and carefully practicing the motions you want to get out of it will generate the neuronal pathways necessary to make that happen. Just be patient with yourself. If you haven't made your offhand do a whole lot for the majority of your life, the fact is that the nerve pathways needed to make it work aren't built up. You have to build them, and it takes time.
Probably more important than that, start working on footwork. Triangle drills and ladder drills are a great place to begin. Fighting effectively is all about moving intelligently. As with your hands, your feet won't do something you've never asked them to do before.
For visual references and to learn some of the basics, check out the videos
on this YouTube channel.
As to your second question, the concept of how much an individual "needs to train" is dependent on what the individual wants to get out of the sport. Belegarth is a game, and we're all here to have fun. Some people want to train and become technically excellent fighters. Some people want to roleplay. Some people want to just goof around and throw silly shots and don't care about being good. Before you consider if you should be talking to someone about how best to enjoy the game, you should be asking them how they want to enjoy it. It would be wrong and harmful to project your own idea of how to play the game onto others.
If the issue with your friend is a matter of ego, then that is also entirely separate from training or technical skill. All of us should make humility a foremost practice, because when we place ourselves on a specific rung of the ladder and say "I am precisely this good", then by nature we are placing others on rungs above or below us. When you then face off against people who you see as being on a lower rung, ego will quickly start to poison your fighting. You'll slough (ignore) shots from those people when you think "that was lucky and I normally block that, I'm not gonna lose because of
that". You'll grow frustrated and angry when you don't beat those people, or when they surpass you. You'll ruin the game for yourself, and your attitude will ruin it for others. This is especially prominent with small groups that don't regularly get out to fight others; it results in "big fish in a small pond" syndrome.
So, my advice here is to first think about how you personally want to enjoy foam fighting, and then think about how your friend is trying to enjoy the game. If you feel that their attitude is harmful (gloating, egotistical, etc.), then you need to talk to them about how their attitude is affecting others.
Finally, you say that you can tell from observing that your friend needs "a lot of work", but you yourself are relatively inexperienced. The way you word your paragraph about him has the air of a master watching the trainees with amusement, waiting to swoop in and show them the error of their ways. That's not the way that you would want your friends to view you, and it's certainly not they way they want you to view them. It sounds like you've already placed yourself on a higher rung or established yourself as the local expert of your group. That's dangerous ground to tread on. Before anything else, you are friends who want to play a game together. Regardless of your relative levels of skill or fitness, you should want to grow and build each other up
together. Don't come at it from a position of authority. Nobody likes feel lorded over or condescended, and nobody will stand it in the place where they voluntarily come to have fun.
It sounds like you've kind of defaulted to leading this group, and that's an awesome position to be in. Every realm needs leadership, and it's rewarding to see people getting joy out of something you helped facilitate. It's also a difficult job, and a lot of it isn't intuitive. I would highly, highly recommend that you read the articles in the "Realm Management" section of the BSK. I started fighting when I was 16 and took over leadership of my realm not long after, so not too much unlike the position you're in, and the articles in the kit that I've written draw heavily from my experiences during those early years. I made my greatest mistakes as a leader in that time, and ultimately it was damaging to my realm and to my friend group. Take the reins and lead, but do so from the position of "I have no idea what I'm doing, but I'm going to do my best to learn." Do that, and you'll make a great leader.
Feel free to post any questions you have along the way. We're all here to help build each other up, and I'm happy to lend what advice and experience I have.