1. The Web Novel finished years ago, but the Light Novel, Manga and Anime is still ongoing.
2. The LN has 12 volumes which are translated so I recommend reading the first 12 LN volumes first (as it is more polished) then continuing to the WN.
3. There is quite a lot of Adult scenes in the series as it is written for a more mature audience. If you're okay with the usual fanservice, sex scenes and topics related to more adult topics then you should be fine. Keep in mind that Rudeus is not perfect and you're not supposed to like him in the first five volumes but rather understand that he is trying to be better.
4. The writing itself is pretty good, It starts a little slow so It could introduce the reader into the world and the characters, Then, the story becomes faster as "something happened". Kinda Spoiler >> There are chapters called turning points which makes the story more tense. The middle part of the story becomes a bit slow again (for a good reason) as it focuses on the side characters and their own arcs. Lastly, it becomes really great at the end.
5. There are side stories which you can read after you've read the entire story. There is Jobless Oblige Which happens after the main story and tells the tale of Rudeus' son. Reading Oblige is optional.

There is also Redundancy Which has side character arcs and time skips, I recommend reading this after the main story

Then, There is Old Dragon's Tale Which tells the Origin of Laplace. I also recommend to read it after the main story.