pediatric oncology

I read over similar forums, however a lot were outdated so I was looking for a more up-to-date answer, maybe from someone who had a similar experience recently. I am only a freshman in undergrad, however I was given the opportunity to shadow a peds oncologist, which is super meaningful to me...

I'm an M2 at a US allopathic medical school. Other than trying to get the best pediatrics residency possible, what should I be doing now to make myself most competitive for pediatric oncology fellowships? I have a bit of clinical (non-hem/onc) research experience pre-med school but not much else.