I'm certainly not trying to scare you off filmmaking. Rather, I'm trying to give you a sense that it's probably not at all what you're thinking it really is. Fan filmmakers typically aim too high from the get go, and their plans are frequently impractical.
This is one reason I recommend things like 48HFP, as they are great opportunities to get experience.
If you have a script, I have a crazy no-budget idea for you: learn by doing.
In short get a camera...and it can be ANY camera—even an iPhone or whatnot—get some friends or any actors you can find and actually go shoot the script...without makeup, props, lights, sets, anything. Then just edit it together (there're a fair number of free editing software packages). Sure, it won't look or sound pretty, but what you'll have done is create the equivalent of pre-vis for the whole film. Think of it as a rehearsal. You'll learn tons just from doing that, and it will cost you not much more than time.
That experience will change the way you think about writing and making movies, period. You'll change the way you write scripts. And if you don't love the process, you might realize it's not for you.
Now, on the positive side, you can sorta go from 0 to competence in short order. I'll use myself as an example. Although I made goofy little 8mm films in high school and did computer animation in the 80s and 90s, my practical experience with making movies was really nada. In 2003 I wrote and directed a sci-fi short subject, since abandoned, where my reach exceeded my grasp. In 2007 I helped make a 48HFP film (as writer), and in 2008 directed my own 48HFP film...the first film I completed. The next year for the 48HFP I made this short subject (link),
which tied for Runner Up for Best Film and won for Best Costumes and Best Sound Design, which just goes to show it's possible to learn to make something passable in a fairly short time if you're serious about doing good work.