R/G, a fine color combination. What’s pulling you towards this? OP specifically mentioned Null Rod aggro. The only noteworthy synergy I can think of with R/G is Spirit Guide acceleration.
Is that the direction you’re taking this? It would be helpful to know if so (so that the suggestions can be tailored to synergise with Guides, or compensate for the inherent card disadvantage you suffer) or if not (so that other suggestions can be made).