Trying this with only 1 mirror wall, works perfectly so far, one loss overall after 2(22F & 23F) floors.
I used Tea mill for the first 2 21F floors and cleared all but 1 mission, and went Dark Paladin fusion deck for the third one(add in that 3000LP gaia card to clear all 3 missions.)
i just did it without SRH to level 30
some replacement i can think of security orbs, sphere kuriboh, curse of anubis (free), rising energy or heck inspiration made some dent for me as well
or add in tons of equip cards that raise the monsters attack to extremely high for easy win, especially with the level 6 piercing damage dinosaur.
I played the deck without the ninja and the level 4 SR dino (was really unlucky with the event).
I just threw in one black tyranno and some other level 4 high atk beater, double summon for easier summoning it, oh I added in one exploder dragon (saved me on occasions when auto duel fails) but that's purely up to you
that my deck by the way, I know it looks really bad, but it still manages to do the job.
I only started a month ago f2p so there's a lot of cards I need and yet I don't have it, so I threw in quite a number of tech cards.
yeah as ridiculous as it sounds I beat it and mostly using auto duel, of course, I didnt get much points but that wasn't my main goal.
well its way better than people who struggle despite having all sort of main meta deck like red eyes / toons / naturia/ etc.