Instant Fusion is quite an old card from way back in 2006. It was released in the infamous Cyberdark Impact set and is one of the better cards from it. Its effect can be easily explained in one sentence: The card Fusion Summons a level or lower Fusion Monster that cannot attack that turn and will be destroyed in the End Phase. The thing with simple cards though is that if they are good at what they do, they will stand the test of time and pop up throughout the game’s history. That’s definitely the case for Instant Fusion.
Earliest sightings of Instant Fusion would let the player bring out Tribute fodder for decks such as Monarchs, however, Thousand-Eyes Restrict was forbidden when Instant Fusion came out. One of the craziest things this card ever did though was bring out Elder Entity Norden, a Rank 4 Xyz Monster. Later, the card would shine in Lightsworn variants due to being searchable by the Predaplant engine. All these examples make the card seem like a thing from the past, but the card has had other uses as well, especially recently. Kaminari Attack proved to be a niche tool in early Thunder Dragon builds and Invoked Raidjin was definitely a nice tool in Gouki strategies.
Present-day duelists may want to use Instant Fusion in Prank-Kids decks to kickstart a massive chain of plays. Invoked, which has always been an under-the-radar strategy, can use the card in multiple ways, bringing out cards such as Millennium-Eyes Restrict or Invoked Raidjin to serve as an extra Link material or to dodge hand traps.
You can definitely play Instant Fusion even if you're on a budget. Out of the ten printings the card has had, five of them are Commons and several of them are currently valued at a little bit more than just a Euro each. A bit higher on the price shelf are the Super Rare versions from Astral Pack 8 (October 2015) and Fusion Enforcers (February 2017). Both will probably still cost you less than having a drink at local pub if you want that simple-but-pleasant modern Super Rare foil. Not much more expensive, but with an embossed name are the Ultra Rare versions from Ra Yellow Mega Pack (February 2012).
The holy grail for this card, however, is the Ultimate Rare version from OTS Tournament Pack 4 (April 2017). This majestic card is no exception to the rule “good Ultimate Rares are expensive” and will easily cost you about 40,00 €. Luckily, that is not the card's only option, so you can pretty much spend whatever you like for an Instant Fusion.
Although it is not seeing play in any meta decks at the moment, Instant Fusion is definitely a card with potential, able to dish out a Link material at a low cost. There are bound to be decks in the future where the card can shine, so it’s not a bad idea to have a few already available in your collection.