A card that I would recommend for a deck like this is Trudge Garden since the tokens it produces trigger the lifegain from your commander or other Soul Warden type creatures, giving you another potential activation. You could very quickly build up a large board state over a few turns.

Lathiel, the Bounteous Dawn might also be worth considering. Since its ability triggers at the end of opponents' turns too, having Soul Warden and other similar cards on the board means that Lathiel will also grow your creatures in response to all the creatures your opponents play. Lathiel combines really well with Spike Feeder to gain you increasing amounts of life at the end of each person's turn. I don't know if you are purposefully avoiding using infinite combos though, so it should be noted that Spike Feeder combos with Heliod, Sun-Crowned to gain you infinite life.

As a couple of budget options:

In the past I've found Intangible Virtue to be very handy in Kykar. The vigilance that it gives tokens makes your combat planning much easier and the power boost to your tokens is well worth just 2 mana.

And while I haven't had a chance to try it myself yet, I think that Embrace the Unknown is worth considering as a value piece. It gives you a repeatable way to trigger a bunch of your cards throughout a game and the costs of your other cards are generally low enough that I don't think you'll have to worry about being unable to play most of the cards that you exile.