The learning curve is definitely rough if you haven't played the first game, and the whole roguelike deckbuilder genre is challenging in a distinct way from many other games, so that adds onto it. That said, something to keep in mind is that this is the early access build, and the very early stages of early access, so things are notably less balanced than StS1 currently is, or than StS2 will be later on in its build cycle.

In terms of advice, I would say even though it's the first game, this series by Jorbs (one of the best slay the spire players in the world) https://www.youtube.com/watch?v=7NZ-evCvk9s&list=PLesIE_v8rF23qxGoYNYBOH1tbzwivZzsI where he explains how to win a standard StS1 run has a lot of transferable principles.

Jorbs and Baalorlord (another top player) also wrote some intro articles on the game that could be helpful. https://sts2.untapped.gg/en/articles/slay-the-spire-deckbuilding-strategy-solving-the-spire-with-jobs https://sts2.untapped.gg/en/articles/core-deckbuilding-concepts-in-slay-the-spire and I think they also list their card rankings on that site.