Play as normal all the way through first, and build up your skill normal mode before attempting expert and especially master. Both expert and master are much more difficult. Even with end game armour, some master mode enemies can pretty much one hit kill you.
The items from expert mode treasure bags are very useful, but won't make a lot of difference if you don't have the experience with fighting each boss.
10 hours isn't a lot of experience (I have hundreds of hours, and still find expert/master challenging) and have only experienced two bosses. Play the game as normal, learn as much as you can for now, and then take that experience to an expert world later on.
You can have more than one world, so you can make an expert one and have a try, but you will struggle, and die, and die, and die. A lot lol.
Take your time, and enjoy the experience.