hmm, ive never personally done a webcomic but im in the same boat as you for wantin to start one, so ive been preparing a bit and gathering tips
it's best to make a rough, point outline that helps you put the plot together
example:

[X] lives in/at [Y], and everything changed when they met [Z]/[Z] happened.

As a result of [Z], [W] happens, kicking off the adventure.

[insert a few vague directions/important events here]

[V] happens, and [X] lives happily ever after/[insert your story outcome]

you can make a rough outline like this as detailed as you want, but if you have specific events planned out (with no buildups in mind/you're writing on the fly), it can lead to a lack of structure and/or the events you want being forced and not as satisfying
at the same time, you shouldnt be super strict and have all your dialogue be set in stone in your mind as you're writing-if you need to/want to change something, then change it
[continued.]

then, the length of your webcomic can be something to account for as well
if you're creating your very first webcomic, it's good to start with something relatively small so you can ease into comic making in general (maybe a simple little series involving every day life problems with your main webcomic characters?)
/then/, if you've found at least a rough footing for your smaller webcomic style, then you'll be able to handle the bigger one better
finally, speaking of style--your art will likely improve as you're drawing the comic, so if you're a person who struggles with backgrounds, pushing through that will help you a ton with drawing the webcomic and also improving your art
these comics can also take a while/can be a little difficult to get an audience for unless you've already gathered an audience beforehand (another good reason to make a smaller one first), so don't be discouraged if it takes a while to actually get traction
[continued.]

finally, one of the worst things you can do is to spend too much time deliberating/planning and then end up never starting it.. so if you wanna start it, then start it!! when you're ready of course

i hope that helped ya in some way! i havent done anything comic related yet since colors is quite tricky to draw comics on, but i'll likely be able to do stuff when it comes out on switch, cuz it'll have more features and all that jazz :0
ok i'll stop ramblin now pfffft