As long as you're aware that engagement can be slow, you should be fine. It's frustrating, but it seems to be something people miss. It seems to have trailed off these days but there are periods where people pop up after only a few days wondering why they haven't got hundreds of subs yet.
The buffer is very important. So many people go into webcomics thinking it'll be fine just draw it and update as they go. Which is fine if this really is just a hobby and you don't care for engagement, but to pick up an audience, consistent posting is one of the biggest draws, so having an amount of the comic pre-drawn and ready to go in case you fall behind schedule for any reason can be a life saver. How much, there's no real consensus, some people got for chapters, some people got for scenes, some people just got for staying a page ahead. It just depends on where you're comfortable, but just do yourself a favour and don't try to make a page then post then make the next page then post, it will lead to burn out so quickly.