How do beginners diagnose conflicts and stabilize Skyrim load order?

[Scarlett.L]

I've played Skyrim on and off for years but never dove into modding until now, and after installing a few popular graphics and gameplay overhauls via a mod manager, my game has become unstable with frequent crashes, especially when transitioning between cells. I think my load order is a mess and I might have conflicting mods, but I'm not sure how to diagnose it properly. For experienced modders, what tools and process do you recommend for a beginner to build a stable, sizable mod list from scratch, and how do you systematically test for conflicts and performance issues before committing to a full playthrough, especially when dealing with script-heavy mods that might cause problems later?