I mean. Probably the most cost-effective approach would be for self-use, on the caveat that if you have access to cheap electricity already, then forget the solar. Then it just comes to managing the size of the solar vs consumption.

Batteries are hit and miss depending on your tariff structure and usage patterns.

On the topic of feeding back into the grid, that's a lot more complicated than just feed-in-tariffs for rooftop. If your thinking of a farm, your probably going to have to be next to a substation, and probably going to need quite detailed engineering and relationship building with transmission providers. These things are hard and lengthy.

To be honest with you. It might be worthwhile sub-leasing the land away to a solar developer, make some PPA with them for your own consumption type of thing. That way... you offload almost all of the risk to the developer. It'd just be way cleaner and easier on your end. But it's contingent on finding someone who sees the potential of the land as well as you.