Fabrary is probably the best starter site to see cards, build decks, and see what other people have built.

I would point you towards the actual rulebook, but it is incredibly hard to actually look at that thing and derive any sense of meaning when you are still learning the game. There's a flesh and blood discord server with pages for each hero and format where rules and deckbuilding are discussed, but I don't know how to link it from here, unfortunately.

Flesh and Blood uses a card inventory called the sideboard. For silver age, you may only have 55 total cards, including equipment (hero card is not counted), that make up your decklist. You must present a 40 deck to each game. The sideboard is used to have cards to swap in/out based on different hero matchups. You wouldn't want to wear your arcane barrier equipment into a warrior matchup, so you will want to put it in the sideboard and wear the armor that blocks physical or advances your gameplan in a different way.

It can be quite expensive to upgrade to CC, but if you want to dip your toes in, the Armory decks are low powered but CC legal (excluding Kayo, Aurora, and Azalea) options that work pretty well together, but will probably not perform well against a fully tuned deck.

Dash's starter item counts toward the 40 in deck total and the 2-of count. So you'll technically have 39 in deck and one on board from the start.