i am thinking of playing this series, i have told its good but i know little about it, how is the gameplay, and should i play them in order and which one is better
what games is it like so i can get an idea of what it is

The gameplay is your standard isometric RPG, much in the vein of Fallout, Icewind Dale, Neverwinter Nights 2 and Planescape: Torment, so you click and click and click. To be honest, the interface is quite clunky and the D&D ruleset takes quite a bit of learning if you're not familiar with it, so Baldur's Gate is not an easy game to pick up in my opinion. Getting familiarised with the basics saves you quite a bit of trouble, although it doesn't make the beginning much easier; until you hit level 4 or so, pretty much everything can kill your more fragile characters in a single hit, and your tanks won't be much better. It gets better relatively quickly, though, you just have to be very careful at first.

The games should be played in sequence; BG2 is superior in pretty much every way, but that doesn't make BG1 bad by any means. More to the point, it's hard to understand what the hell is going on in BG2 if you haven't played the first game.

I would advise you to follow those instructions:
http://www.gog.com/news/enhance_the_gameplay_in_your_edition_of_baldurs_gate_from_gogcom
You can then play the first Baldur's Gate using the enhanced engine of the second game. There are a lot of things that were improved so it's a really good idea. Furthermore you don't have to install any additional content if you want to taste the vanilla version on your first playthrough. This is what I did and it worked pretty well. By doing this you are able to play through the whole series smoothly - you will realize when Baldurs 2 begins but barely ;)

As for the game... it's a masterpiece, no doubt about it. It is, however, a very long masterpiece ;) It takes a lot of time to complete it. IMHO the game starts very slowly and it is pretty annoying. It takes forever to get to the second level. In terms of experience, not chapters, because I was already in third chapter while my hero was still level 1.

The game is definitely focused on the story but you won't progress far without combat. It takes some time to get used to it but then it works pretty fine. I will also add that combat is entertaining and rewarding (especially those hard boss battles)

What can I say more? Go for it!