So, Trinispheres effect says Add 3 mana
For just one mana, you really cant do much better
Deharme Standard Legal Alchemy Legal Pioneer Legal Historic Legal Modern Legal Brawl Legal Legacy Legal Comp
Cutthroat Contender can trade life for a temporary boost in power, Fake Your Own Death gives +2/+0, Antagonize a whopping +4/+3, Daring Escape +1/+0 and first strike, and Riveteers Initiate can gain deathtouch
One other interesting area of note Imperial Seal and Vampiric Tutor are ideal for showcasing the importance of card advantage vs card quality
The much-hated Propaganda, which means enemies have to pay to swing at you, could make for a good addition here too