This is OTT but,
California's economy is ranked sixth largest in the world. We have our own ports, we produce almost half of the fruits, nuts, and veg for the entire nation. We also have a thriving dairy and beef cattle industry. We also have a great deal of oil offshore as well as wind and solar farms. And a thriving tech and manufacturing business base . Our population is 38.8 million, about half the population and about twice the size of the UK (just for general reference). We are the 46th state least dependent on federal money. California is in a much different position than the Southern States when they seceded. They were almost a completely agrarian economy and had to import massive amounts of raw materials and manufactured goods. And they had to fund a war, something I hope we'd be able to avoid!
I think we could succeed as a country very well, but it would be a great upheaval. Federal jobs would be lost or forced to relocate (mine would have been included!), programs defunded, there are federal lands that would have had to be dealt with. I don't even know how that would work. Would we just 'claim' Yosemite et al as now belonging to the Republic of California or would we have to make some type of payment for federally owned lands and buildings. Bottom line is I expect it's much more complicated and expensive that we can realize.
But as I say, it won't happen. The Constitution makes no provision, creates no 'path', for a state to peacefully secede from the Union. And this has been interpreted to mean that it cannot be done without amending the Constitution to create a way to secede.
If any of you are interested, here's a good article
www.washingtonpost.com/news/the-fix/wp/2016/06/27/so-you-want-to-secede-from-the-u-s-a-four-step-guide/?utm_term=.9f7fccb9a1f2