That's a difficult question to ask because there's not a solid answer to give. I think the best episodes are those that are long enough to get through a whole idea or plot point or whatever and leave off at a satisfying break off point. For some comics, that might be one page or a few panels even (see gag-a-day strips that have 2-5 panels often time). For a more story driven comic, that's usually every few pages- looking at my own comic as an example (it's a 70ish page short story) I think my episodes would ideally be broken up every 5-7 pages for the best reading experience, as that's the duration of many of my scenes.
Buuuuuut a lot of beginning and hobbyist comic authors opt to trade off length for upload speed and consistency. I know many many many comics here on Tapas have a 1 page per week style upload, because that's about as much as many authors can produce in that span and waiting around to build up a "complete" episode can take a long time and mess up your posting schedule. With my example above, I'd be able to post 1 update every 2ish months if I waited for a whole 7 page episode to be done first. Instead I do the 1-2 pages per week thing (1 usually, 2 if one of the pages only has a few panels or not much happening).
The other factor to consider is that to be visible on sites like Tapas or Webtoons, frequent updates are typically more useful for than than beefier ones. Focusing on Tapas for example, you can appear on the "Fresh" section of the website and the "Sort by upload date" section of the app once per day. So theoretically posting a bunch of 1 page episodes will expose your comic to more eyes than doing only a few longer ones- with those you have to hope that the right people are looking at those lists at the right time to pick up your comic. There's something to be said about quality, which is one advantage to longer updates. Especially over on Webtoons, folks seem to really really prefer longer updates to shorter ones, even if they take a little longer to come out. It's hard to say if the gains of putting together those longer episodes would offset those you get by being on the "Fresh" equivalent there.
Upload Frequency is a whole other thing. The only real answer is "the more often you post, the better" but for most people it's unrealistic to post several times a week unless you complete a bunch of work up front. Once a week isn't great but at the same time is pretty standard. Some folks opt for every 2 weeks or once a month, others manage to do 2 or 3 uploads a week. Really depends on what your schedule will allow.
One last note on buffer- definitely try to make more than you think you'll need lol. It's hard to say, 10 pages may be a good amount for you, but as someone who peaked at that much buffer, give or take (I think I had 8 weeks of buffer updates) and ran out of it after a short break and never recovered... I would borderline recommend doing more xD Really up to you though! Another thing to think about is- regardless of what your regular update schedule ends up being (1 page a week, or wev), think about if you want your very first episode to maybe be longer to draw readers in. I started my comic out with a big 7 page update (got all the way through the first scene) because I figured if I was someone reading my series and I clicked on it with only 2 or 3 pages up to start, I don't think it would have hooked me. But I think getting all the way through that first scene set the mood for the series and was a beefy enough chunk for people to dig into and make a decision. If you go that route be sure to factor that on top of your starting buffer 
Best of luck beginning your series 
