I'm personally someone who doesn't collect, I used to play the TCG and started a break fairly recently, though I've had a lot of friends who are collectors.
The advice I've earned from them is typically that booster boxes are a lot better right after the set in question comes out, as prices on cards will be higher and buying single cards is a lot less viable of an option due to stores or other people not owning the cards for a set that came out two days ago.
Whenever my friends buy packs or boxes, it's always just for fun, to see if they get something nice and typically just for the resale value to a lot of the players in our area, where if a collector friend of mine pulls something rare they already have, they'd pass it to me if it's a card I need for a deck. It's great to create relationships with close people like this, the more they're involved in the game the better. As a player I've made marketposts before and I'll always show my binder to collector friends first since they're contributors to the binder itself. As a person, I'm more likely to give a card to someone who's supported my collection and my deckbuilding rather than some collector who I've never met before.
I think the most important part is simply trying to establish yourself in a community, and it helps especially if you're just searching to make friends because you can easily get both just by being a supportive person in the community, whether it's local or online.
Becoming part of a community, especially with a lot of people who are collectors as well, helps a lot with getting people to trade with. One of my collector friends is really close to someone else who collects and they'll just sit around for a few hours at a local league and discuss trades between each other, or what cards they've been able to get recently. It's a trading card game for a reason and trading is the best way to get specific cards you're after, since you aren't directly spending money, and you're getting exactly what you need instead of cracking thirty-six and hoping for that hyper rare.
Basically, see if you can get single cards if you're looking for specific things, and try to trade for them if possible to save money. Buy booster packs if you're looking for general things like starting a collection of a new set, but keep in mind booster packs get worse and worse with your odds of earning something you want as a collector, especially if you're going for full sets.
And the most important part is establishing yourself as part of a community, which makes it easier to connect with people and be able to earn cards in these ways. This site has a buy/sell/trade section and while I've never been a part of it, I know some people are here just for that, so it might be a good way to start.
Good luck with your collection!
~ VioletValkyrie
