While I heartily agree with @Galastel's answer, I'd like to focus on what can make the 'four parallel storylines' work.
First of all, a word of advise: the more parallel storylines, the more difficult it is to craft a concise tale. I'd say that, to pull it off successfully, two is great, three is ok, four is borderline, five requires an exceptionally good writer.
Next, make sure each storyline has a protagonist that could carry an entire tale by themself, whether you intend to make them the MC overall or not. This means that, when you're in the shoes of each one of those characters, they feel and act like they actually are the MCs (after all, we are all MCs in the stories of our own lives). If the reader gets the feeling this is a secondary character with little impact in the tale, it'll be harder to get invested in that character.
Bottom line: it's not an MC and their three sidekicks; it's four MCs, though one will develop to become more important. The other three, however, should never be dropped into mere secondary: they must have their own worthy arcs resolved. In other words, you have three MCs and one MMC.
Introduce the characters as early on as possible, each one within their own chapter. It might be a good idea for the chapters not to be overtly long, but it's not a must. You want the readers to feel a bond to all of them. If the characters become opponents at a later time (say they both vye for the same romantic interest), the reader should feel at least a bit torn about who to root for.
Remember that what you have is effectively four novels in one. That means you have four stories that could stand on their own. If the characters' goals remain different, and they all have their worthy arcs to fulfill, then the novel will be long and may work best as a trilogy.
Alternatively, the four parallel stories can end up weaving themselves into a single one. Imagine four characters who set out independently but which have a common end goal. They end up meeting and working together, effectively turning four stories into one. This means the individual arcs will be resolved more or else in tandem and the novel as a whole doesn't need to become that long.
But say that the characters have not only one main goal which is common, but also a secondary goal which, once the main is solved, will lead them to break up or even become antagonists to each other. The story would have started with four parallel stories which united into one only to unwind themselves into four again as the characters's goals become increasingly different.
I used some of these techniques with a 'three parallel stories' novel of my own. The catch is that all of the characters will be MCs at specific times throughout the novel, and each will affect the others' lives both knowingly and unknowingly. The first three chapters were used to present the characters so as to help the reader create a bond with them. Then I focused on the MC of the first section of the novel, dropping a few references (where appropriate) to the others.
So far, the feedback has been positive, as the readers liked the three characters and, while enjoying the tribulations of one, are looking forward to reconnect with the others. Eventually, the three plots will be wrapped into a single one, then unwrap into two.