The most important thing.
Everyone who starts a magazine has definite passion in their respective genre and have certain idea about their audience.
The one thing they wish they know, sometime after starting out, is that striking a balance between the content that users like to read and what investors (ads) like the viewers to read, isn't always easy.
To get ad investors, you have to have audience and to sustain the audience, you need to have the investors' money.
Think it through.
I wish I had known that Steve Jobs would die early and any vision he had for the iPad and the re-birth of magazine publishing would die with him. It is an amazing device but iTunes sucks as a platform. Plus, as long as Medium lacks paywalls (or something similar) and lacks an embedded payment mechanism, there is no good solution.
But if you want to cry over spilt milk, schedule a few minutes and we can sit on the ground and share sad tales. {grin}
You are David facing a Goliath of distributors, retail chains, and competitors. Print fewer copies than you think you need to start and send distributors fewer copies than they ask for. This is especially true for large distributors, some of which charge you by the pound for taking on your title and are, therefore, incentivized to ask you for many times more copies than they will actually sell. The second hard truth is that you will initially have an exceedingly difficult time selling ads due to the low circulation of most independent magazines.
By now, you are starting to see the picture that running a magazine is more complicated than putting stories to paper. The reality is no independent magazines survive on the traditional model of magazine and ad sales. Consider what differentiates you from other publications for a particular set of business customers. Monocle realized it was its high-income audience and has used advertorial content to position brands for its readers.
You can read more here: https://medium.com/swlh/how-to-start-a-magazine-f510f14566c5
Besides if you do have any questions give me a call: https://clarity.fm/joy-brotonath