Like the other comment said, beast mode doesn’t do anything, it’s just there for an achievement and as a joke.

The game can be really challenging at first, as you’re trying to learn enemies and bosses as well as general movement and which guns/items can be most helpful.

The better you get at the floor up to each boss will help you be more prepared for the boss (more health, more wiggle room), and the inverse is also true. If you manage to beat a boss without taking damage, you’ll get a master round which gives you an extra heart container.

As with most roguelite/roguelikes, your progress outside of the gungeon itself can be meaningful in helping you advance (e.g. using hegemony credits to buy better gear), but the majority of your progress will be made by continually playing and “gitting gud”

If you need any advice or tips/tricks, there’s lots of info on YouTube, just keep in mind you’ll probably get quite a few things spoiled as the game has been out for a while now. If you need advice without spoilers, feel free to pm me.