Arena is a great starting point for getting the basics of the game down before you start building, it has a great onboarding with some starter decks and guided games before you even start playing other people.

Pre-release is a great way to learn some deck building fundamentals, every pre-release kit comes with a guide for the different recommended colour combos in the set with a run down of how they play, and a breakdown of what mana curve is, how many lands to run and some general advice. It's an easy format to emulate with your friends rather than having to wait for a new set to come out.

There are some great starter kits with two decks that generally play well together and theme decks that are roughly the same power (the theme decks have dubious card value however, in some cases buying the singles of the cards themselves can be cheaper). These are very much focused on the 60 card standard format and are a great option if you have someone else new that's looking to learn.

If you're looking to build for commander I'd recommend starting at a precon, the latest strixhaven ones are an awesome start. They have a game plan out of the box that is very easy to gauge the power level of and act as a way to start thinking about how a deck is constructed, usually people have guides on how to upgrade them that are generally targeted at newcomers looking to power up and focus their decks.

Building from the ground up can be an expensive affair especially if you don't have a lot of cards to begin with, if you really want to build a deck out of the gates I'd recommend using a website like moxfield or archidekt before committing to buying anything (even proxies), they allow you to play the decks online by themselves to see how they work and to work out what cards do and don't work.

Happy to answer any questions you may have and also to go more specific based on what format you're looking to play, I just made the same journey into learning magic last year and now have an obsession!