As of now the witcher 3 is on sale here on gog, my question in should i buy now the base game or wait and buy the goty that is quit expensive ?

GOTY because its have witcher 3 + all dlc's.For sure it will be cheaper than game plus expansion pass

Is it okay to first play through the main game and then buy the expansions or is it better to have the expansions installed before starting to play?

You can wait to install the expansions, if you desire - as you cannot start HoS until close to the end of the main game anyway, due to the level requirements.

My preferred method is to play the main game, then the expansions - and then start a NG+ and play through again. In this way, you will have much of the added content of the expansions already available in your NG+

Whichever way you decide to play through you are sure to enjoy it.

Hi,

GOTY is same price as a 50% discounted Witcher 3 + Season Pass: 49,99 (in Netherlands)

If you prefer to own the boxed version, then wait a few more days, if not, then you can buy W3 now, and the SP whenever you like.