Am I right in thinking ragdolls are quite a big breed? 
My top tip would to get something as tall as you can accommodate. Most cats like being up high (so they can look down on you!) A lot of cat trees look okay online but are tiny in reality! They are dwarfed by an adult cat. I'd find one that's at least shoulder height especially for an indoor cat. The footprint is already established so you might as well have an extra level or two!
They're also notoriously wobbly. I've purchased a Trixie wall bracket for mine (about £5) which keeps it nice and stable as puss leaps up the platforms. You can actually get cat trees that go from floor to ceiling and secure at ceiling height.
I found the ones with caves/ boxes a bit pointless as my small-medium sized male can't fit in! So that's a bit of a wasted feature unless you have a kitten. I've tried waving a feather-on-a-stick toy in the cave only to be met with a look of disgust, perhaps a cursory swipe if I'm lucky.
The platforms aren't really big enough for the cat to stretch out annoyingly. Mine tries to arrange himself but struggles to fit! I've seen the odd cat tree with larger, square beds with a edge which look fantastic. I'd like to replace the top platform with a larger one in due course.
I have the Trixie Alicante:
here
I purchased a separate hammock bed from Amazon which I've added next to the second-from-top platform. The cat absolutely loves it and sleeps in it all the time. It's given the cat tree a new lease of life.
He goes up on the top platform from time to time as it's next to a small pantry window and allows him to survey his kingdom 
I inherited gingercat as an adult cat and he shows absolutely no interest in scratching the posts. My leather furniture is FAR preferable 
Zooplus, Amazon and Ebay (Buy It Now but also worth checking local auctions, I've seen some really good condition secondhand ones on there) are good places to look.