I think the answer depends on a number of individual factors:
1. How content you are with your comfort and competence after qualification as an Open Water diver? Further training might be a suitable choice if you still felt that you could make improvements in your foundational skills that would improve your enjoyment and/or safety in diving. Do make sure that YOU are happy with the level you reach on your Open Water course...qualification should be joint student/instructor decision. This is about doing more training at your current level - not training to increase your level of diving.
2. Access to quality rental equipment after qualification as an Open Water diver?? This is pretty obvious, but if you cannot rent decent equipment, then you won't be able to dive. So, investing in equipment might be something you need to do. This depends on your locale and the diving industry there. There are benefits to owning your own gear - like familiarity, comfort and reliability. Do a lot of research if buying scuba kit.
3. Access to suitable diving opportunities in your local area? Again, this is very location dependent. Do you enjoy the diving in your local area, or will you reserve your diving only for occasional trips/vacations to more comfortable diving destinations? Forcing yourself to dive in conditions you might not enjoy can be counter-productive to your enjoyment of diving. There's nothing wrong with being a holiday diver. If you didn't enjoy local diving, then you might be better served using your time/money in the short-term to do more training or get the equipment you need.... and save up money in the long term to get more diving vacations.
4. Are there local diving clubs or can you get a local diving mentor? Clubs are a good way to dive locally, or for people to enjoy shared-passion vacations. Many clubs will have regular pool training, refreshers, development etc. Or you might find a more experienced diving mentor who is willing to help you develop as a diver on local dives.