If cost is not an issue then I would recommend a CSA naval invasion of California.
I have experimented with a naval invasion of Cali a bit. I once tried it in a PBEM, but my opponent quit the turn I landed so I didn't get to see how disastrous the plan was.
I think you would need at least two divisions, probably three, to assault the Cali forts. I've tried to sail there asap to beat the spawning of units from the early Union events, but it can't be done. An assault would be necessary, I don't think starving the fort is practical because of your own supplies and the difficulty of blockading the ports.
Getting the gold mines in Colorado and Nevada should be doable with just rangers. If you build them all as soon they show up in the build pool you will end up with more than if you waited (events will create rangers and remove them from the build pool.) A pack of 8-10 rangers led by someone like Shelby will rip through any of those small western militias. You'll also never get a better chance at effectively using the ambush special order, so, it can be pretty fun. Though, the ranger strategy relies on using your demonstration cards to flip loyalty in regions you want to capture.