Pay close mind to what Teleportation Circle can flicker, and consider Dungeons, because theyre not only good value, but a number of rooms let you target Agrus to put +1/+1 counters on him (and vis-a-vis the team) with only the two mana to copy the ability
If youre interested in adding hard infinite combos, here are some options you should consider
Fabled introduces 33 new cards, fresh mechanics, and reprints of fan favorites for collectors and players
Despite this, Amethyst has one of the most competitive mechanics in the game, known as the Bounce effect
Oliver only had a single Teferi in the sideboard, so he could have played four instead of adding a color if he just wanted three-mana planeswalkers, but Oko is enough better to justify adding another color and playing a maindeck Breeding Pool in his Jeskai deck