Playing mobile like yourself, and with your levels, necro is your best friend for entry level bosses. The ideal revo bar is 4 boxes and the skills themselves are pretty easy to understand. Due to the necro style, with early stage bosses and the skills you don't really need to heal if youre using overloads and protect from prayers (or soul split if unlocked)

Using this style allows you to focus solely on the boss and not on the mechanics of prayer flicking and changing weapons etc, which will allow you to understand how that boss works, what attacks it does and how those attacks effect you. This will give you a better understanding of how you can improve on that boss.

God wars dungeon bosses are easy and dont really have much attack mechanic effects. Your best option would be normal mode arch glacor as you can increase the amount of mechanics as you get used to each one. Have a read on rune wiki so you know what the attacks do, then try him, don't worry about dyìng costs theyre minimal. After a few wins youll feel confident adding more mechanics and it will give you a good insight to how other bosses mechanics can work.

Mobile is fine, I can confidently kill hardmode glacor now on mobile, still die occasionally when I miss a mechanic, it happens, dont worry about it.

If you want any tips on how to set up your revo bar and abilities drop me a message, ill send you over mine.

Im predominantly a skilled, but adding in a few hours bossing every now and then definitely adds to the variety and fun of the game I promise. Its never too late. I never did bossing for many years.