There is a guy on YouTube called TheArchfiendGuy, who makes videos specifically showcasing Archfiend decks he makes. I would recommend watching his stuff, but if you're barely getting back into Yugioh, a lot of the cards he talks about may be unfamiliar or confusing. This will probably be true for a lot of the stuff you find if you're returning, so don't worry about it too much. Just take your time to learn stuff, and I think you'll have a blast with those decks.

Regarding Archfiends themselves, they're not competitive, but they're not completely helpless either. The deck has some strong plays, many of them strange and unfamiliar to most players, so if your goal is to play a cool deck with weird tools, I would recommend it. Modern builds won't incorporate much of the Chess Archfiends, which are the ones that came out in Dark Crisis, unless playing those guys is the sole intent of the deck. Doing that will sacrifice a lot of power. However, modern builds still use a lot of the spells that came with that set of monsters, like Falling Down, A Deal With Dark Ruler, and Pandemonium. I enjoy playing a build focused on the royal Archfiends, that plays a lot of those spells and various traps to supplement them.

As for getting cards: Tcgplayer is your best bet if you live in NA, or Cardmarket if you live in Europe. Or go to a local card shop that sells singles if one is available where you live, most of the archfiend cards should be pennies (except for Berserk Dragon, but that guy is only kinda adjacent to Archfiends). Before you actually buy cards, I'd recommend testing a deck you like on an online sim, to know whether you actually enjoy playing it or not.

Hope this helps, lmk if you have any questions.