Notes & Combos
No Seahorse Carrier package here in favor of making room for more high value Effect monster tribute fodder. Masaki could be used instead of Celtic Guardian but I'd favor it over Masaki for the 1200 DEF against Piercing damage. Alternatively you could run Thunder the Thunder, but you're not really short of ways to break thru boards here with the Skill/Umegumi/Speedy Performer/Seraph. (Celtic Guardian also has superior meme power, let's not forget that)
The idea behind not running the Seahorse Carrier engine is that you'll statistically see more games without it then you would see games where you can use it, so your overall card quality in your deck is diminished by running the wimpy Bubble Era vanillas. So instead, run more cards of better net quality than just the 3 Carrier + BE vanillas and hope that RNG is just going to favor you more that way. This'll probably be more true as we see more better cards to run as well.

To be honest I absolutely did whale for this deck entirely, although there's nothing stopping you from buying it with just gems as you've noted.
If there's anything I forgot to add to the notes, it would probably about the ratio of bosses in consideration with the rest of the deck; you want those valuable spells/traps, but you also want to be able to consistently proc your skill so you want more bosses, and you need to keep a tight 30 to hit it big with double Kimeruler direct lethals... really, just don't brick I guess.

No Seahorse Carrier engine or Kuribots makes it less appealing. I guess it could be a soft-4th copy of any boss, but most games end before that should matter. It could grab things off mills too I suppose. I'd rather have another copy of Dark Ruler Battle Slash though. Feels good to pop the Widespread Ruin.