There will always be a correct one for your deck, so its hard to fit one on this list
You may know me from my podcast with Javier Dominguez and Andrea Mengucci, Competitive Magic with the Karnies, from my World Championship 2023 run to a semifinals finish with Golgari Midrange, from winning the first Australian Regional Championship, as the team captain of Handshake Ultimate Guard for the latter half of 2024, or as a clown who enjoys impersonating Lee Shi Tian at premier events
Combat Celebrant is one of the cheapest cards on this list and a fairly easy way to get an additional combat phase
Technically, Frontliner adds two power to the battlefield for one mana, but we need at least one other creature on the battlefield for this to work
Back then it was $2,000.00 usd and was selling fast so that was the right price
Since you have such a high mana curve, there are other ways to cheat in creatures onto the battlefield and avoid paying their mana costs