What I typically do when a new set comes out is to buy 3 to 4 "boxes" of the set (around 100 booster packs). Over the next couple of months I'll draft the set with friends or we will do casual sealed tournaments etc. (You need 24 boosters for an 8 man draft or 6 booster per person to run a sealed tournament.). There is a group of us who get together every fortnight or so to play limited like this - usually over a few beers.

By the time I've opened all the product I generally have copies of most of the set's staple rares and I can trade or sell anything I do not need.

It is a sizeable chunk of cash upfront if you specifically want to play constructed you can acquire 'singles' in pieces and build towards a deck over the season that way. I do not play standard at all. I'm a big eternal format fan (especially Legacy). Once you acquire those cards you can play with them forever.

One thing I have noticed is a lot of eternal format cards are getting thrown into supplemental sets (i.e True Name Nemesis, Shardless Agent, Council's Judgement, Containment Priest, Dack Fayden) stuff like that. Which tends to spike the price.