Certifications/learning while waiting

I dont think there is anything that would make sense taking before school (although dont you need BLS for school? If you dont im pretty sure you eventually will)

But I think by/near the end (not before) of nursing school you might want to consider ACLS and PALS (assuming youd want PALS if you plan on going into peds/OB) since these could certainly make you more competitive in the job market (its not exactly easy to get a job without experience/if you dont know people in high places)

Theyre both somewhat pricey and only good for like 2 years or something, but id possibly consider taking one and or both around/in your last semester of nursing school. Since youll probably want/need some knowledge in pharm + nursing before taking them (and again theyre expensive and expire in 2 years ~)

If math is not your strong suit, I'd do a math refresher course.

Medical terminology

English skills (grammar, punctuation, sentence structure)

Pharmacology

Foreign language

Don't bother with medical certifications beyond BLS. You'll have to recert them later, you don't be using them in school, and no one will really be that interested in your certs as a new grad, because you will clearly not have applied any of the knowledge yet.

Don't bother with PALS if you want to go into OB- you'd rather have NRP and the AWHONN fetal monitoring courses, but again, wait until you get there.