Depends what you mean by "ergonomic". A lot of the tricker/weird ones end up being bad for a lot of people.
But as for getting a really good quality chair that you can adjust for comfort - that's worth doing. I have a Mirra. It was a hefty investment even with a discount (bought from the same supplier as my workplace at the time, who happened to buy Aerons by the dozen), but with a 12 year guarantee works out better than a string of crappy cheap chairs.
I don't think you have to go crazy though, just use something height-adjustable with back support. Before the Mirra I had a simple gas lift office chair that was probably 20 years old by the time I pensioned it off. It happened to support my back at the right angle.