Edit: TLDR: thumbnail panels > edit > thumbnail pages > edits and writer's approval > sketch pages > more edits > ink and color/gradients > hopefully no more edits
I work with writers so I don't write my own scripts. Since I usually work with chapters and not episodes, I ask them to write the whole chapter. Some give very detailed scripts panel to panel, some just dialogue and vague descriptions of the scene here and there, some prefer a novel format. So I usually make a first sketch of all the panels and which ones will have dialogue after reading the script. I do this on the same canvas(simple square panels with stick figure level drawing) so I can see how many of them there are.
Then I organize them in pages, in a way that the action is easy to read, and all pages have something interesting if possible. If I already have the average amount of pages chapters should have I try to match that amount when distributing the panels, if not I decide it roughly on this stage.
At this point I reread the pages a few times to edit the panels, delete or add things for clarity, edit the dialogue if I think it's too stiff or doesn't match the character's personality (editing the dialogue in this stage is important, because if I have to add or change something I'll usually have to change the whole panel and thus the whole page, better to do this in the thumbnailing stage than when I have the whole chapter sketched, or worse, if I'm already inking). I send this to the writer for any further edits and approval and after that is done I start sketching the finals.
I usually sketch 5/7 pages in one sit, and ink around three together (cuz I get bored of staring at the same page, also you can just draw the character in all panels first, then focus on all backgrounds, etc).
I make the speech bubbles(typing included) in the sketching stage as part of the panel composition and it's the first thing I ink.
Thorough all stages I modify panels, sometimes I even discard entire pages if I notice I don't need them, but I try to keep length of chapters consistent. I color/put my graytones after or during the inking process.
Also, my sketching to inking process takes several layers haha like, I start with a very rough sketch, I start inking but notice something off with the pose so I correct it on this "inking" layer, rinse and repeat at least three times per panel xD