'so im planning to cosplay ochako-' ZOOMS IN ur doing gods work
when i cosplayed todoroki i got the blazer and uniform first and then, like you say, i just had to get iidas wig and glasses and boom! i could cosplay him (which i enjoyed thoroughly, hes absolutely my favourite) too. the same goes for the training uniform, although i dont have one of those. you'll be recognized in both of those, so just get whichever you want, and get the other later if you want!
whats important is you enjoy it!