I can try to answer questions 1 and 2.
- Campaign mode is basically a step by step introduction to playing in Frontier Mode, the Free to play subset of Modern. You will earn new Frontier cards that can be used in Frontier or Modern.
- Focusing on Frontier will allow you to build a low level free Frontier deck and when you are ready you can also try Modern using the same Frontier Deck. Modern rank play is a new and a lot different than Frontier ranked play.
Thank you so much for this explanation @gregory-f! That makes total sense now. Really relieved to hear I can build a deck through the Campaign without needing to dump money into new sets right away. Gonna focus on finishing Book 1 tonight!
Buying the Frontier set will also be good. It's a lot cheaper than other sets. They're easy to max if you don't have time to play in the Frontier mode.
Thanks for the tip @logen9f! That's really assuring to know that there is an affordable market route to speed things up. For now, I'm actually enjoying the Campaign mode, but I'll definitely keep that in mind once I start leveling up my deck!