For me, the first film is almost perfect.
I also don’t think that Fennec and Boba coming together (or “the Book of Boba”) is somehow important for the stringency of the second season movie or further movies!
Season 1 and movie: We get to know Din’s job, and how he gets with Grogu into conflict about it and wants to save him.
In the process, he builds friendships with others (Cara, Greef, Kuiil, IG-11).
Season 2 and movie: Din searches for other Mandalorians to bring Grogu to his.
In the process, he learns about other Mandalorians as well as Jedis, and some of the black lightsaber is all about.
Season 3 and movie: Din helps Bo-Katan to conquer Mandalor, at the same time they get on the track of a larger intrigue of remnants of the Empire (Gideon/Thrawn), and try to defeat them with his grown network of friendships (Boba, Fennec, Bo-Katan, Greef, Mayfeld and maybe some new ones)?
Season 4 and movie: ? (Maybe Din and Grogu come a last time together again (also Ashoka or Luke), to defeat Thrawn/Gideon finally. Grogu dies in the end maybe…)