What do you consider the basics? Blocking, holding, execution? Or more advanced techniques like slow escaping, fuzzy guarding and throw punishing? In any case, the best practice would be offline against real players but for the basics you should be training on your own.
If you think you've got the basics down, playing against the AI at level 6 (not 7 or 8, it makes them inhumanly reactive!) could help you apply the basics. Online/offline against players is mostly there for improving your mindgame, not necessarily applying fundamentals.
Pictured and JAIMY speak the truth. You cannot learn DOA5 properly online. Offline, your fundamentals will develop gradually over time. I practice against the Level 8 AI and it has help me out immensely in my fundamentals. Playing the Level 7 AI would be a good idea IMO. Have you checked out my guide? It might have some tips that could help out: https://files.acrobat.com/a/preview/2cc9307a-88b6-49e5-a3a2-bb59981ce603