Well, what you’re asking is an entire workflow, out of the scope of what a single forum post should aim for. We can point you towards a couple of tutorials that go into it, but you’ve said you have seen a few already.
Do you have a specific issue when you’re trying to use an image texture with subdivision modifier? That should work, it’s the best approach to achieve what you’re after. You can use micro displacement and displacement modifiers with lots of geometry. Walk us through your set up, post some screenshots, we can spot any mistakes and get it working.
