Kind of a tragic way to turn me off of the series but I'm not skipping any games where the story is that complex. Or does it matter, those of you who are MGS fans?
V is the continuation of the story started in Metal Gear Solid 3, which is a prequel set in the mid 60s. Whilst there are some nods to what would develop in the present, you don't lose anything for not knowing that.
The story continues to Peace Walker, set 10 years later in the mid-70s. Its hard to recommend it to a non-MGS fan because of its availability, it's on the PSP with fiddly controls or vastly improved on the home consoles, but included in the HD collections and Legacy Collections. That said, I firmly believe Peace Walker HD and using console controls is worth the price of the HD collection alone (you get MGS2 and MGS3 in there too, along with the original MSX games of Metal Gear and Metal Gear 2 in the MGS3 menu). The collection can be bought for cheap fairly easy these days (around £20), bear in mind it has effectively five games on it.
Snake's story basically ran from MGS1, 2 and 4.
The games also detail Big Boss' story, which is all set before MGS1; MGS3, Peace Walker, Ground Zeroes and it will end in MGS5, showing how he becomes the villian shown in the original Metal Gear on the MSX.
I'd recommend anyone who wants in on MGS5 to grab the HD collection for as cheap as they can and concentrate the most on MGS3 and Peace Walker. I'm fairly sure Ground Zeroes is now free on certain networks too and this acts as a 'pre opening credits Bond mission' for the rest of MGS5.