>>530110672
>Support cards
They help you "discover" skills or make them cheaper, you use skill points to unlock these skills. The cards also give you extra bonuses when upgradred but don't worry about that as a new player.

>Career or story?
Do career, get the hang of the game and what strategies you like using

>Do I roll for anything?
If you don't know what you're doing obviously not. You should read character profiles and see if you would enjoy having them in your roster for like, 5 months. If not just skip and borrow meta units for cheap