I plan to make a more extensive topic on this later, but essentially each ship type has a “follower cost” to add to your fleet. What this means is that you’ll need a certain amount of inactive followers (inactive followers are ones that currently aren’t occupying the seats of one of your fleet ships) in order to add it to your fleet. Just off the top of my head cost for each ship is as follows:
Sailboat - 5 followers
Caravel - 8 followers
Ketch - 14 followers
Brig - 32 Followers
To get more followers, you can set your fleet commander’s task to Patrol (labelled “Plunder” if you’re negative renown) and you can also go around sinking ships.
Fleets take a lot of patience, it’s an investment that will require a lot of time and money but also has the potential to save you a lot of time and give you money as well once you’ve become acclimated to it.
Only your 4 Command ships will, your vice-command and lower ships won’t
The “Power Level” indicated at the left of the screen increases passively as your fleet progresses. All the level affects is the max durability (Hp) that the ships in your fleet have. The “Fleet Rank” at the top centre of the screen is the more important one, because at Rank 5 you unlock the Conquest task (collecting dark sealed chests) and at Rank 10 you unlock research (which is where you get rewards like the fleet raven etc.)
This is how my fleet is currently looking; with all the knowledge i’ve acquired from testing fleets for months, it still took me around 6-8 hours to simply get a full lineup of Brigs in my command and vice-command slots. (Ketches are also perfectly fine, I simply use brigs for aesthetic reasons).
I wish you the best of luck captain, happy fleeting 