I got the goty edition off humble bundle, and the previous two games are pretty cheap, so should I play those before playing this?
Thanks in advance.

If you can, yes. It's not absolutely necessary, but the three games form one continuous story, so you'll probably enjoy the whole thing more if you play them in order.

if i were u - yes

Yes.

Do you need to? No. Should you? Absolutely. Why not?

Play Witcher 3 just for fun.

Puzzled?

Play Witcher 1, this is the closest one to Witcher 3, actually you still won't understand the tension between the mages and the northern kingdoms, the Nilfgaardian empire, the events after Loc Muinne.

Oh hell still puzzled?

Play Witcher 1 and 2 before diving into Witcher 3.

Say goodbye to your social life, or wife, husband? Dog? Cat?

Just be aware that all three games play differently. Sort of like Mass Effect where they changed the rules (and gameplay mechanics) on each game. Witcher 1 is hardest for some but I found it the most fun with true pc interface. Witcher 2 had a butchered interface (compare to 1) but they improve and simplifieid some mechanics and improved the story telling (clearly a larger budget). Witcher 3 they slightly improve the interface (over 2 but no where as good as 1) and witcher 3 seems to have the most 'bugs' or oddities (things like standing next to your horse but 'e' won't mount it unless you look at it at just the right angle); the story telling is best in witcher 3 and while some game mechanics are improved (such as potions) the glitches (most likely due to console emphasis) are the worse. To be honest D:OS and wasteland 2 were both able to offer true pc interfaces at a much lower budget so this is quite annoying.
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Anyways I found the story confusing (even having played all three games) but 3 does a very good job of explaining what you are doing and why so probably ok to skip the first 2 but if you are going to play all three then might as well as start with the first.

Btw it will take a while to get used to the 1st mechanics - while it has the best pc interface the mechanics are new and they don't always work as expected. Its a good game but (at least for me) it took till act 2 till i really got the hang of things.