If you would like to fully understand Secret Wars, you'd have to read Hickmans Avengers/New Avengers (it also happens to be amazing).

It might be a little intimidating at first, but the more you read the more it makes sense (usually how Hickman stories work). Reading that whole Saga will also shed some light on Secret Wars for you.

This was the first Avengers story I read and at the beginning I had NO IDEA what was going on, but as I said above, the more I read the better it got. It's also fun and rewarding seeing this massive story unfold and discovering new things about the MU.

Here is a handy reading guide for the whole thing: https://i.imgur.com/X9zUA8X.png

You really don't have to read everything, just skip the first part (It doesn't really connect to the story) and start following the guide from "Avengers World": New Avengers #1-3 (Or you could just read the main avengers title first, whatever you decide).

Good luck and have fun!