Borderlands 2 question - unlocking all content

If you want everything - it's probably the best idea to buy the GOTY edition (owning the base game is not a problem). I think it's the cheapest option, but remember that it doesn't include the Headhunter bonus missions - they're released later. Also the skins must be bought separately.

But you may consider waiting some more - Borderlands 2 was on a bigger sale few time already.

The best and cheapest way - find some good and trustable trader. That will be cheaper for you.
As example: Borderlands 2 Game of the Year 22,49€($31) in store or for 12€($16) from a trader. Can you smell the difference?

Season Pass for the 4 campaign addons (and it also has UVHM upgrade 1 on it), then UVHM upgrade 2 (digistruct peak one), then headhunter add ons I guess. Those are the DLC's I got, and they are better than 'skins' :)

The headhunter ones (1 2 and 3 at least) (4th is coming next week) will disappoint you since they are basically about 30 minutes long (maximum) with no replayability (but skin rewards for doing it I think)

EDIT: Player characters eh, well I got gaige since I preordered the game before, but the best classes are the default 4 anyway, but do get gaige if you feel like it :)

GOTY is a much better deal by far. The Season Pass and Psycho or Mechromancer Pack costs only a penny less than the game of the year edition, and GOTY has so much more stuff. Buy that and you'll be all set. And even though you don't need the Headhunter Packs, you might wanna look up some reviews to see if they'd be worth it to you. I personally think all of 'em are a good buy for 1.49. They're quite short, but they're at least a buck fifty worth of fun.

My favorite Headhunter pack is the TK Baha one. ^^

If you own only Borderlands 2 base game the best deal is to find a GOTY for cheap, also if you want all skins and/or DLCs not included in GOTY you will have to buy them on good sales.

if you want to unlock all the achievements, you have to buy the GOTY edition.

no GOTY edition, you can unlock only 50/69 achievements

Retail BL2 might be available cheaper and keep a look out for sales from other sites (GMG had a sale a month back 75% off I think), other than that not much else to do since there's no upgrade to GOTY >_>

apart from buying on sales ,I think firstly GOTY and then whatever is missing.

As most people have already said, GOTY is the way to go. I would keep an eye out for Green Man Gamin's site, too, because they tend to have prices that match Steam's.... However, with some discount codes (that are usually found in the page itself on a banner or on sites like Kotaku) the price can drop a little bit more...

I bought the game with the season pass long ago, and I haven't run out of content yet... I actually have run out of time to see all the content. Therefore, I don't think the headhunter packs can be THAT important. Still, if it's worth it to you...

Well I will just mention again like rest of the people that GOTY is the way you go.Now about Skins...well you dont really need to buy them all at once..I mean look at what you have,check skins somewhere else and then decide(i personally got 3 skins for my psycho) .Just have in mind that torso skin decides what color will be your helm. For headhunters packs...yet to play them(waiting to see will 2K put them in their own package at reduced price since 4th headhunter is coming up) but as far as I heard they are quite fast to complete yet bring quite a few of new stuff in it. So at first place go get GOTY,complete the 4 DLCs and then look for headhunters.
Have a nice day.
Edit: Actually GOTY doesnt include the 2nd upgrade pack so you may consider getting it too.

Come to think of it, aren't there more dlcs planned? What happens then? D:

As mentioned by most everybody here, the GOTY edition is probably your best bet to get the majority of the content for this game. You can then look around for traders who have the Headhunter packs and other miscellaneous DLC for somewhat smaller prices, or wait for those DLCs to drop down in price (and as AkibaStitch mentioned, GMG usually has pretty good discounts on these games, in conjunction with their voucher codes, which usually give you 20% off the already discounted price. It's not a lot, but a discount is a discount.).

Personally, I'm just going to wait until 2K decides to re-release BL2 with every bit of DLC when the stop releasing them in April... which probably means I'll be waiting for several more years, on top of the 5 or so years I'll have to wait while I either find a computer that can run this smoothly, or get a PS3 or 360 :P

OK, I'd like to thank everybody for their input, it has really helped me a lot. I've decided to go the GOTY route. It adds a lot of content to what I already have and I'll get the rest with time, it will probably be cheaper in the future as well.

As for the GOTY itself, the rate my buds and me are playing this, we have new stuff there to probably last us a year, literally. Seen about a dozen offers for 7 keys (some even for 6), which I think is a good deal, so I'll take that.

Cheers and good luck with your giveaways!