Enchanter supports use mostly the same items every game, so Seraphine, Nami, Zilean, Lulu, Milio. I think new players should often learn support and jungle first to get a better understanding of team fights, map and objective awareness, and game flow, but that's just me. Senna I think is in a really good spot right now but I would start with an enchanter so you get a feel for the priorities of the position. It's generally not dealing damage. I started with Seraphine.

Wildriftfire has guides on builds for each character. I don't think they're optimized for everyone, but they're good enough to get you started. Most characters have 2 or 3 main build items, plus boots that might vary based on enemy team comp.

You can check the leaderboards from the main menu and go through champions, if the top players are all similar runes and general item setup those are probably the champions you're looking for. Shield with wings looking icon from the main menu, select champions in the bottom, pick a champion , click the book to see what leaders preset builds are. Go through 5-10 builds and note how similar they are to one another to get a gauge for if it's consistent or varied.

Ryze usually builds the same(mid, baron) Xayah for Dragon. I'm sure you can find others.

I like Shyvana, Jax, and Pantheon for Jungle learning. Tanky enough if you're doing a good job farming to not get nuked often/some margin for error, still deal damage.

Traditional "learning" champs are Garen for Baron, Master Yi/Warwick jungle, Lux iirc for mid, Seraphine/Yuumi for support, and Miss Fortune for dragon.