This is a deck I created to auto-duel L45 standard duelists to win quickly and hopefully get 2-4 chests. Did a lot of tweaking over a couple of days when I'd lose a duel and this is the end result with what cards I have available. BC would be a lot better than SOrb.
1x Sphere Kuriboh
3x Des Kangaroo
3x Big Koala
3x The Earth - Hex-Sealed Fusion
2x The Dark - Hex-Sealed Fusion
1x Fusion Sage
1x Super Rush Headlong
2x Security Orb
Master of Oz
Video of the deck in action:
I did swap out the third Koala for B.E.S. Big Core basically for an easy tribute and protection while I get the fusion together.
I also pulled 3 fusions and 3 koalas after the video so I felt I needed an easy tribute that could survive a couple turns.
Lvl 45 feels overall about the same difficulty as lvl 39 duelists, only "The World of Oz" deck is causing me trouble. I had to build special deck to counter that and cannot auto-duel it. So yes, I recommend raising to 45 to gain 1 more duelist. But wait for some others' opinions, too.