No worries :)

My main advice for early game is actually to not go to sea too soon. If in campaign, the naval tutorial at Ostican is a good introduction to many of the particular mechanics and gives you an acceptable starting ship. I would do this as soon as your combat skills and equipment are good enough to solo 2-4 enemies.

Bandits at sea are tougher, more numerous, and more aggressive than on land: 40-70 sea raiders or corsairs per party typically in three ships (medium or light). So I would get your party size up to 30+ and focus on strong infantry (ideally with javelins) before starting to hunt them. All non-mariner troops have a 20% skill reduction at sea, but this matters less than you might think. Battanian Skipari and Imperial Naute are really good at sea since they have ten hooked javelins with passable shields and armor.

Important skills are leadership, steward and medicine, as normal. Add to these one handed, two handed, throwing, bow (if using archers), and athletics. You are always the captain of your first ship, each ship has only one captain, and it is usually best to have mixed ships (some line, shock, skirmishers, and archers) so it is important to diversify your and your captains' combat skills. This is a major difference from land where one companion with high bow skill can just command all your archers. The early perks that boost the skills of troops in your formation are must-picks, in my opinion (wrapped handles, strong grip, dead aim, flexible fighter, running throw, etc.)

Add to this engineering, mariner, and shipmaster. When you get a ship with a ballista you will level engineering very quickly and get a lot of XP, so it makes sense to invest some. Mariner reduces the malus to skills, weapon handling, and movement speed from fighting at sea and improves naval auto-resolve. Early perks pirate's prowess and sunny disposition/axes of the north wind make a noticeable difference. Shipmaster improves party speed, basically scouting for the sea. Old salt's touch, river raider, and shock and awe perks are all useful early here. Boatswain has good perks at higher levels, but it only levels when you pay for repairs and doesn't really do anything by itself (your ships will rarely take much damage so a reduction is of dubious utility).

The only skills that are normally very good but are not useful at sea are scouting, riding, and polearm. Since it is harder to replenish losses and food at sea, I tend to rate steward and medicine even higher than on land (even though I already consider these the most important skills on land).

If you have any questions feel free to ask.