Start small then snowball - I’ve started floristic mostly identifying plants very nearby me (my game was to findback all species in my village), because you need to known well a “base” of plants - then when you’ll seen another close species, your brain will send you the message “oh this one is like species B, but habit looks odd and it blooms 2 weeks later”.
iNat also helps me a LOT being able to pratice during winter and taking a look to the closely-related taxon in areas i would have never been gone. Once you start understand a genus/group with field experience combined to the internet ressources, related features will become a lot clearer (bc in most flora you actually need to know the plant to really understand key features).