As someone who used to play MtG pretty aggressively myself, sorry for the PL, me and my group when playing at home and building our own decks always just ordered the specific cards we wanted. Buying the packs can be fun and you can get a super valuable card (sometimes), but unless you're playing in a draft or doing an at home draft buying the booster packs is usually a waste of money and you end up with a lot of bulk cards you'll probably never use. I guess if you wanted to collect as many as possible?
The most popular formats (pretty sure they're still most popular) are standard and commander, and with both you typically have a set theme and plan for what you want your deck to do and how you want to win, so it's cheaper usually to just buy the cards individually. While having a large collection of cards satisfies the consoomer instinct it's normally just a waste of money, and it's a pain to go through and organize them.
It's also fairly common practice to just print fake cards out when you're just going to be playing at home to save on money. If you want to play "officially" or at a game store or something, or enter in an event obviously you use real cards, but there's no reason not to use proxies at home, especially when you're in the process of building a deck and haven't figured out what works best. To sum it up, Kevin's wasting money, which isn't a shocker.
I just woke up so apologies for the rambling.