Resources are plentiful (imo) so you can easily buy all of them as you go, the biggest progression blocker will be not having stuff unlocked so just focus on doing the assigments and upgrade whatever is possible, prioritize unlocking higher difficulties and weapons you use. Picking and choosing is pretty much only a thing when it comes to skills, cosmetics and cores.
Once youll be able to do deep dives you should know what to do at that point.