Accelerating the move towards a cloud infrastructure - how do you decide / what applications go first? Which are top of the list for you currently?

There are a bunch of frameworks from Gartner to help with this such as https://www.gartner.com/document-reader/document/4023205?ref=solrAll&refval=442438896 I would use a framework to help organise those applications.

Quick answer, those best suited with features that make them most “cloud ready”, that can do so at the lowest cost.

Factors like data readiness (nature of data, encryption, and the like would also play a role).

Apps that are about to require a major investment in time or money should go first:
- in need of hardware upgrade
- in need of a major software or architecture upgrade

As mentioned above, apps that would benefit most from scalability/elasticity should also be prioritized.

The more legacy  (and heavy) an application is, the more beneficial it would be.

The ones that will benefit the most from the elasticity and scalability of cloud infrastructure. Lifting and Shifting a traditional n-tier monolith will result in increased costs and subsequent frustration.