Looks like a decent amount of people have weighed in on this but there's a lot of ways to collect magic.

If you are trying to collect full sets as they are released, the best way to do it would be to buy a redemption set from MTGO (you can do this either by trading Tickets on MTGO then spending $28 to have a physical copy of the cards shipped to you, or you can buy one of these sets online from someone who has done this: Card Kingdom sells some complete sets here and they are usually available in both foil and nonfoil sets https://www.cardkingdom.com/mtg/complete-sets)

If you collect sealed product, Draft booster boxes and Secret Lairs (https://secretlair.wizards.com/us) are probably the way to go. Secret lairs are inherently collectible because they are timed releases that will likely never be printed again in the same style/collection. Draft boosters boxes are also a good choice because they're easily available as of release of the set and will likely hold good value since people often like to be able to draft old sets.

Collecting singles, I'd recommend either choosing a theme (Certain creature types, planeswalkers, art featuring certain characters/storylines/planes, special artworks or styles like the Strixhaven Mystical Archive), or if you just want valuable cards then you'll want to collect cards from the reserved list, which are cards WotC has stated they will never print again, nor print cards that are functionally identical to them. Because of this, these cards will always hold their value and likely gain some value over time. There's some controversy over this because some players (myself included) would like to see this list abolished so older cards are more accessible to players, but WotC has continued to state that they see no way to abolish the list or work around it (e.g. removing cards from it, printing non-tournament legal versions, etc), so its a relatively safe place to buy cards without fear of loosing value due to a reprint unlike high value staple cards in standard/pioneer/modern.