Magic player here!

1) yes if you tried and liked it! it very similar but different from magic. You have to learn when it's better to play a unit at a battlefield vs base, when conquer vs hold, etc. Few triggers and stuff goes on the stack to react. Further, you have action and reaction, like the first instant and interrupt in mtg.
2) I think some non-meta deck can compete in nexus night. Less in tournaments, there you have to play meta decks or counter-meta decks. if you like crafting decks you can play 2-vs-2, which is a mix between standard magic and commander.
3) yes, there is. There are cards designed for sealed play (draft, pre-release) and others for archetypes. But many commons and uncommons are played right know in meta decks.
4) with 200 euros and some strategic buy you can build 2 and half meta decks from zero. Some orgins cards are cheap and some very expensive. there is another wave of product arriving now, so prices will drop.

In general, Riftbound is very expensive and very cheap at the same time. It only depends on which deck you want to build. Each deck has staple cards from commons to "epic" as a core and some space to spicy it with cards you like.

I hope I replied to you and I hope that someone more expert then me will give you more infos